Mike Bosworth's two books Solution Selling and CustomerCentric Selling talk a bit about RFP/RFQ's.

The authors note that most RF[PQ]'s are prewired and biased towards a preferred vendor. The client gives out the RF[PQ] so the client can say it was properly competed for so it can pass the approval process in upper management. If you are not that preferred vendor who was there from day one, you will most likely not win.

The author cites one anecdote of a big company that has a separate department that only handles RF[PQ]s. One day they decided to take some metrics over a time period. Out of that time period, they submitted 153 bids to unsolicited RF[PQ]s ... only won 3.