I'm describing what I saw from many governments and comittees from when I used to review these specs for bidding.

I would have to disagree its not the norm, governments are always corrupted in some way, but thats a much more divergent discussion.

I can say with confidence that the overwhelming majority of specs are written to include or exclude specific bidders though. My work is and was global, too, so this isn't a US only issue.

How much they do to control the bidders list will vary though.