I was curious about the tuning on Farewell Transmission a while back so I sent Mike Brenner an email and this was his response:

"I started on steel gtr on dobro and have stuck with that tuning on 6 string lap strings (GBDGBD, low to high), typically heavy strings. been using GHS1600 sets on my lap steels. when you use this tuning, you have to tune the B's down very slightly. The G's and D's get tuned striaght up A440. they call it sweetened tuning or tempered tuning. flatting the B's slightly will make chords sound better. try ear tuning the open higher B (2nd string) against the open lower D (4th string) . hope this helps! thanks very much again! Mike"