Well, I tried that link, it wouldn't give me any results.

But I CAN report my own experience: I have a quite old Sanyo SCP-3100, running on Sprint. Wednesday evening, I made a number of calls from the summit, but on "Roaming" mode (connecting to a carrier other than Sprint, but with some sort of agreement of cooperation with Sprint).

It would ONLY connect from one spot ...close to the edge at the summit, pretty much due north of the northwest corner of the hut. (From the corner, walk north to the edge without gaining or losing elevation. I could see the north wall and the west wall of the hut from the point.) Also, it would NOT connect if held close to my ear. In fact, if I tried that during the call, it would sometimes disconnect. I had to hold the phone away from myself and use the speaker mode to carry on the conversation. But in that setup, the calls were clear!