Actually - if someone with the technical skill and necessary access to the network (an "at work" IT staff member) had decided in advance to trace activity for the "at work" network to FR it would be VERY EASY to determine exactly what had been posted and who had posted it. I believe that activity would be quite illegal unless it was done at the direction of a manager with sufficient authority (an illegal wire tap) but it would be rather easy from a technical perspective.
I doubt it would be illegal if it was coming from the employer's end (State of Maryland).
Your post provoked me thinking again.... I do know how relatively easy it is to gain access to a specifically "not listed" number. I'm wondering, if the internet gets taxed.. and all "lines" are thereby under a public entity jurisdiction.. won't this mean ISP identifiers are more readily "located"?