According to archived pages, I was able to narrow down the return of 1709 to service to around late August/early September 2017:
http://web.archive.org/web/201708221551 ... rg/roster/
(from 8/22/17, shows the 1709 in testing)
http://web.archive.org/web/201709091357 ... rg/roster/
(from 9/9/17, shows 1709 in service)
By any chance, do you know what happened with 1706? It was rebuilt and brought back to service earlier in the year, but was involved in a collision with a car at a crossing, I think in Bridgewater in either April or May. Haven't seen it on any tracking app since, but it's still listed in service. Are they holding it at BET or is it being used for non-revenue purposes at the moment?