I would say they will not interference with each other. I am not sure though. So I checked out some google pages and came across this website
Check out this comment:
[quote]Comment by Radoslaw Kornicki on January 24, 2010 at 1:25pm
I had no issues with none of my sensor readings when using xBee. Actually I’ve used it in such configuration from very beinging, I’ve never even hooked up this board directly to the PC serial port.
I also had no problems with getting a propper GPS lock. Of course the xBee on the picture is just for tests - final version will use different module with a wire antenna.
I think in the end the trick is that I have separated the sensor circuit (analog) portion from the digital one, they have separate voltage regulators and signal tracks are placed as far apart as possible on the board (I also use a 4 layer board - this way I could ground planes to isolate possible noise). In the early tests I had lots of noise comming from the PWM inputs and the servos themselves - optical isolation did a great job dealing with that noise.
As to the mounting in the plane - I have nice spot in the wing of the plane - no interference with cables and etc.[/quote]
Note that he has used separated power supplies, separate circuits and the signal lines are as far away as possible.
I am not sure if this will help you, but it might give you some tips though.
I do not have a compass otherwise I would try it out for you. (I own the 60mw xbees)
Note: you can also configure the 60mw xbees to send a less stronger signal.