Most of the tenants in the ESB occupy fairly small blocks of space. As a result, the building has a multitude of tenants - the lobby directories are quite a sight - rather than a few big ones, in contrast to the situation in most other major office buildings.
Few if any of the current tenants are government organizations. As far as I know, GE never had space there.
"Let me think about it" = the coward's way of saying "no"