I worked in the AV industry - not at Cruise but based on incidents like this and other things I’ve seen from riding in Cruise cars - they absolutely need a cell phone connection and will strand or pull over (or stop in the middle of the street) if there’s anything more than a very transient break in remote connectivity. Fundamental parts of the stack assume that if there’s any uncertainty in a situation, a remote operator will be available to clarify how the car should proceed. The car can’t make certain safety or operational guarantees without this.