How can I deal with interference from a test RF signal (XM radio) in order to get a live RF signal of the same type?
There are few possible measures you can take:
1. As suggested by pjc50, ask the manufacturing team to attenuate their test signal. They can use either a fixed attenuator or a variable one.
2. Install an XM band repeater at the software department. This is a more expansive solution. Sirius/XM offer one at http://shop.siriusxm.com/xm/ctl10600/cp49750/si4025848/cl1/ However, it is very likely that the repeater will capture the manufacturing floor's signal.