As for bike lockers, it might depend on locations but at my company at least there is a lot of process around the lockers, intended to keep them from being places where bombs could be located. (part of the post 9/11 security concerns is my understandding)

the basic restrictions are:

No overnight or long term storage, day use first come first serve only
everyone has to use work supplied locks that security has the master key for.

Security actively checks that the lockers are empty at night and cuts off non company supplied locks and removes contents on a regular basis.

and my company is not a super high security military supplied or anything like that..... just your basic PLD semi company.