As I said elsewhere, most of this is known to employees of these companies, and privately mentioned, but not highly public.

This is done because otherwise, the towns get yelled at. Heavily. There are lots of interest groups involved in this kind of thing.

It's hard to make an argument with private/secret evidence.

It's not secret, just not very well known. As I said, you can usually find it in mountain view committee meeting minutes (for Google), cupertino council minutes (for Apple), etc.