I don't know anything about the BMW SOS button but many such services have a way to test it without sparking an actual emergency call. You call them and they put you in test mode and you activate it to see if they received it.
Many, many years ago (the 1980's) I was a project manager on a DoD program called the SARSAT AFRCC (Air Force Rescue Coordination Center) automation platform at Scott AFB. The system detected aircraft ELT signals and EPIRB signals and correlated the location with other verifications of an actual incident. More than once, I'd be hanging out in the rescue coordination center and watch them respond to a guy that intentionally set off his ELT on an overdue route of flight to see how fast the Air Force would respond. Let me just say that when they scramble the Civil Air Patrol, local law enforcement, and other SAR resources the bills could be quite large, even back in the 1980s. They had no sense of humor about that at all.
I was once listening on a speaker phone when the local sheriff located an ELT going off in a farmer's field. It apparently had been placed there on a battery power supply to see if anyone would come looking for it. With the sheriff on the phone, he asked if he should shut it off and they responded that he should. The next thing we heard on the call was gun shots and then him asking if it was still transmitting. Fun times.
'16 R1200GS Triple Black
'16 KTM Super Duke 1290R
'18 Yamaha WR250R