I used to work for a couple of different issuers. For one, we pulled according to geography, in a single acquisitions campaign we would have customers with records from each of the 3 bureaus. For the other issuer, we were much smaller and only used TransUnion but then switched to Equifax when we had an issue. When I left, we were negotiating with each of the 3 to see who would give us the best price if we gave them all our business.