The article doesn't mention which satellites or which satellite provider is used. But Apple invested $450 million in Globalstar. https://www.apple.com/newsroom/2022/11/emergency-sos-via-sat...
This article from LeMonde seems to imply that they're using Globalstar: > "To offer this new feature, Apple had to integrate a miniature antenna in its smartphone. It captures part of the signal of satellite constellations without relying on a satellite dish or a specific telephone handset. The iPhone manufacturer signed an agreement with Globalstar, one of the operators of low-altitude constellations, sets of satell…
But I am pretty sure that is a LOT more bandwidth than what will be used for highly compressed text messages in emergencies.
[0] https://www.globalstar.com/Globalstar/media/Globalstar/Downl...