To enter a switchgear / MCC room to gather info for readings what would the requirements be under NFPA 70 E.

All of the panels are buttoned up and secure, typically our operations wear long sleeve shirts, pants (all fire retardent) safety glasses and hard hats when making rounds.

What kind of readings are you referring to? If it is just reading panel meters, there is no special PPE required.

Article 130.2(A)(4) of the NFPA 70E 2015 states that "Normal operation of electric equipment shall be permitted where all of the following conditions are satisfied:
(1) The equipment is properly installed.
(2) The equipment is properly maintained.
(3) The equipment doors are closed and secured.
(4) The equipment covers are inplace and secured.
(5) There is no evidence of impending failure."

If these conditions are satisfied then there is no need for additional PPE. You can also refer to Table 130.7(C)(15)(A)(a) which states that there is no arc flash hazard during normal operation of circuit breakers, switch, contactor, or starter if these conditions are met.

Great but without doing an inspection how do you know that it is properly designed and installed?

Second, how in the world can you know that it is properly maintained? Hint: Article 300 which references NFPA 70B and NETA MTS is not really much help. And those standards aren't either...just try implementing them. Plus those are maintenance and/or testing standards, NOT necessarily a safety standard. The requirements are different depending on your goals.

I recall several past responses from the 70E Committee that stated that just walking by does not constitute an arc flash hazard. I study all the OSHA cases for 5 years to get a good idea of what causes an arc flash. In 2 cases, a cover that was being removed slipped and fell into live equipment. In 2 cases with almost no details, it appears that operating a breaker might have initiated an arc flash. In a 3rd case the equipment was improperly maintained and switching initiated the arc flash. In every single case although it might not have been the "employee's fault" that initiated the arc flash, I did not uncover any cases where "just walking by" initiated an arc flash. But there were several cases where employees were doing what would be considered for lack of a better word, "normal operations" which would not normally in and of themselves be considered hazardous.

It is pretty easy to understand in the vast majority of cases why an arc flash happened. There were several cases where workers were drilling out energized busbars to drill and tap to fit a different make/model of circuit breaker in a panel. The drill contacted the casing and caused an understandable arc flash. In several cases as well using a low voltage meter on a medium/high voltage circuit turned the meter into a fuse and caused an arc flash. So none of these for lack of a better word should be any surprise because they are clearly risky behaviors, and they are relatively easy to identify. I'm more interested in the "normal operation" behaviors that turned into arc flashes because these are harder to identify and address.

Misread...this is for entering the room. Multiple times the 70E Committee has stated that just walking by does not constitute an arc flash hazard. The likelihood of one happening spontaneously is extremely low. Hence even in the definitions in 70E, one has to be interacting with (ie, doing something with/to it) equipment to be a hazard. This is where things like dropped tools, poking/misplacing things, moving something accidentally...the sorts of things one wouldn't expect. The really scary stuff is that there are multiple OSHA investigations where someone decided to drill out the bus bars in the back of a panelboard in order to install an incompatible circuit breaker, WHILE the panel is energized. Or there was the case where someone "fixed" a hole in the panel by loosely sticking a piece of metal inside the panel. When the door was opened, it fell in. Or many, many similar incidents where screw drivers, wrenches, or other tools are left laying on a ledge or against some equipment where they roll/fall in...

This is vastly different from just walking into the room or walking by.

I've been involved in the rebuild of a few medium voltage pieces of equipment where someone was just "walking by" (thankfully not too close) and an arc flash occurred. In ALL these instances water ingress was the initiating cause. One case occurred because of a leaking swamp cooler located directly above the switchgear room (indoor gear isn't water-resistant), but all others were on outdoor equipment during heavy rain. So just walking around might be dangerous if equipment (even non-electrical) is in bad disrepair.

This is the fundamental challenge. Several times there have been attempts to tweak the wording in 70E to acknowledge that "just walking by" is not a hazard. However the sticky issue is how to word it. How do we generalize this to other tasks? It quickly gets pretty hard to explain every conceivable scenario. So we have four cases to consider:
1. Can the current cause fibrillation or other lesser hazards? If not, skip down to step 3. The general rule is 50 V but there are lots of edge cases and exceptions.
2. Is the equipment insulated, isolated, or guarded in terms of the task considered? If so, then there is no shock hazard. If not then shock hazard boundaries apply (limited and restricted approach boundaries, or "unnamed" and MAD for 1910.269).
3. If an arc flash occurs, is the hazard greater than 1.2 cal/cm2? If not then no arc flash hazard exists.
4. Are tasks that are occurring likely to cause an arc flash? If not then there is no arc flash hazard. If there is then the arc flash boundary applies.

Note that we have two hazards to consider: shock and arc flash. For each one we have to consider whether it is likely to happen in the first place, and whether or not the hazard is great enough to take steps to either avoid it (for untrained workers) or prevent an injury from happening (for trained workers).

Note also that 70E still has some issues here. 50 V is still the only "cutoff" for shock...no provision for high voltage/very low current systems. Second in terms of arc flash there really is no attempt at all to recognize that a lower cutoff exists. 50 V has some vaguely worded statements asking the end user to prove a negative, something that is extremely hard to do.