Quote from vulture:
Typically, creditors will use different CRA's depending upon geographic location. For instance, someone in Texas opening an account at Chase might have their TransUnion score used, while Equifax might be used for another state.
It's been awhile since I've tracked this sort of thing, but a site called Credit Boards.com has a spreadsheet where users input their location, their real FICO score, the Creditor and finally whether they were approved and with what credit line.
The forums are also an interesting read into how these creditors just shut down credit lines, cut credit limits, etc. I noticed this sort of activity in a meaningful way back in the summer of 2007, several months before it was widely accepted we were in a credit meltdown.