272.1 was used last season when I saw them in Quebec.
I also heard them pass their VHF backup frequency on that freq just prior to taxi. At that particular show, it was 116.0 (that's right, in the navaid range) and probably varies from location to location. There was no traffic on 116.0 during that show following a brief check-in by each aircraft prior to becoming airborne.
They've also been reported on 242.6, 246.5, 289.4 during practice.
Enjoy their show!! They put on a good one!
-Jim