The HBAL callsign does refer to the Loon balloons, but it is also used for these experimental balloons. Its not for Google's Loons exclusively.
Further, looking up the registration number associated with HBAL0296 & HBAL308 (N256TH & N258TH respectively) shows both registered to Raven Aerostar in Sioux Falls, SD.
Regarding those HF/VHF frequencies, are they used with the balloons or are they for different projects? With only a handful, its easy to monitor them and try to find out (assuming they're in the clear).
WQRI680 is licensed over on the east coast, covering PA, WV, VA, DE, and DC (plus parts of others) as a class FMA1 which is an aircraft flight test station. WQRI681 is class FAT which is flight test and it looks like its at a single location (their base, I presume).