For 11 shows over three weeks in February 2003, Billy played guitar with Bob Dylan during Dylan's tour of Australia/New Zealand:
1. see Feb. 2003:
http://www.trevormidgley.com/GiggingBands.html
2. see first 11 tour dates:
https://en.wikipedia.org/wiki/Never_...003#Tour_dates
Dylan tends to keep musicians long-term. Tour to tour, there's not much turnover in his band. It would appear, therefore, that Billy was an emergency fill-in (perhaps Charlie Sexton pulled out last minute and Dylan had to scramble), or that something did not work out.
I saw Dylan later in 2003 and the guitarist who replaced Billy (Freddie Koella) was absolutely incredible.