[Lucius Cornelius Sulla]

I've been in plenty of high security federal buildings where cell phones are allowed.

Allowed for non government employees? I am surprised at that. I agree that the electronic interference is not likely, I only included it for the sake of theoretical completeness.

[freeandfreezing]

Allowed for non government employees?

Yep. As an example, many federal courts allow cell phones in the building, although of course they must be turned off in the courtroom.