I looked at a bunch of units last summer from these guys, lots of them are lease returns that are not car lot worthy generally pretty well to far gone for my tastes.
My buddy ran one of the BC franchises before it became what it is now. He is still a repo guy.
You do get what you pay for. Most are miled out, or high hour vehicles. Some of it is true repo vehicles that they have contracts set up for through different financial groups. Those ones are the typically the ones to look for but they don't last long.
Very few have any factory warranty remaining, so if you are looking at something, especially a diesel, give it a good inspection first. You might save $5000 but then have to replace the injectors 1000 miles down the road.
Look for any signs the truck has been sank, pull the corners of the carpet up and look for rust.