On twitter someone said one of the WBCN streams is still there while the other was indeed killed off.
The WBCN stream that's still on is the "WBCN The Rock Of Boston" stream, also on 98.5 WBZ-FM HD2, a fully automated stream that CBS has on to continue the "sound" of the mid-1990's/2000's decades of WBCN.
The WBCN stream that was taken off the air yesterday was the "WBCN Free Form Rock" stream, also on 100.7 WZLX HD3, an eclectic rock based mix from the 1960's through today, that was programmed (and live hosted mid-day weekdays) by Sam Kopper, the first long-term rock Program Director of WBCN from 1968 into the '70s. There were some other live paid hosts, recently including former WBCN DJ Dave Wohlman weekday afternoons.
It's rare for a station that broadcasts only in HD radio and online to have paid live air staff, but because it was owned by a for-profit corporation (CBS), air staff had to be paid per labor laws. However, there was very little advertising, so I doubt the station was even breaking even for the payroll expenses for the very small staff it had, and it had probably been losing money all along.
Perhaps there may have originally been hope that HD radio was going to be better implemented and marketed, and that the subchannels would eventually be on more equal footing for consumer access as their parent stations, but that never happened.
