There other thing, as I've learned from other FRS/GMRS forums, is that output power is much less important than antenna height. Given that, is would not surprise me that relatively low power cell phones communicate fairly well with cell towers, which are typically positioned at strategic high-point towers in the area. Radio-to-radio reception would be MUCH MUCH worse unless the users are in line-of-sight, such as one of them on a high building or on top of a hill. In an urban area you'll be lucky to get more than a couple of blocks distance.

Heavy duty radio users (GMRS and hams) focus very heavily on antenna height, placement, and design as a first priority for direct transmission (not bouncing the signal). The power is secondary.