The Volvo I was going to buy was indeed a salvage-rebuilt title. It had front-end damage and was issued a salvage title in New Mexico. Current owner bought it and brought it to Traverse City, rebuilt it, and applied for-and-received a rebuilt title. However the guy apparently "rebuilt" it in his backyard. He most likely used bottom-dollar parts for things like the headlamp - which basically I'd have to replace again anyways - and is obviously not very tech-savvy, thus having nothing but water in the radiator.
I really don't know how Car Fax works, but it definitely catches any title changes - that DMV-related information gets intercepted. Dealership repairs seem to get intercepted as well - the Car Fax that I pulled on this car showed various repairs by the previous owner, including shocks, a taillight assembly, and brakes. I would tend to think that any kind of corporate/franchise repair shop that uses a nation-wide database is probably intercepted/farmed as well. But if you have Billy Bob repair your car in his garage behind his house for a few bucks and a case of Bud, chances are good Carfax won't know about it.
The Volvo dealership who inspected it commended me on spending $100 (inspection and carfax report) to save $4000+ in repairs!