I tried the new XR9 at 912 .....,when the Motorola is runnig it still shuts me down.
Since you are running 3 sectors, I assume you must be running in 5Mhz channels...
Motorola - 8Mhz Channel Width
XR9 - 5Mhz Channel Width
Since there is a 1Mhz channel spacing on the canopy, we must assume that it can bleed up to 1 extra Mhz beyond it's rated channel width, making the upper boundry of which it will interfere 911Mhz
Since the XR9 when running in 5Mhz channels, on center channel 912, goes down to 909.5Mhz for data purposes (see my other post about how far it actually bleeds down to) you have 1.5Mhz, or 30% of your channel being overlaped by the canopy signal. The only thing you can do is to switch to a higher channel (already in use), or one of you must change polarities.
I would suggest keeping the XR9 as you're going to want the extra noise handleing abilities it is claimed to have (just got them yesterday, haven't done any outdoor testing with them as of yet)...