Interesting idea. There is coverage in Yellowknife as long as you're with Bell, and I believe that Telus has started to provide some service there too, lately. On the ice, though - nothing at all. You'd only need to head a few KMs out of town on the Ingraham Trail and you'll never get any coverage again until you go over the north pole and start coming back down the other side! Nothing at the mines or camps.
I used to have a girlfriend who lived about 18 Kms north of Yellowknife on the Ingraham Trail and there was no cell service at her cabin there, but she was in a small dip and I seem to remember her saying that on the top of the hill there was a weak signal.
A portable tower that you towed on the ice would be super cool! But, I know how things work up there and as soon as you implemented that they'd introduce a new rule banning the use of cell phones on the ice road.
I don't know whether Unique458 has a smart phone or not, but I hope that he'll drop us the odd line from YK if he has the chance.
Ride Report: Canada North to South 2008 here
Drive Report: Ice Road Trucking 2005-2011 here