I suspect an image problem. I receive 800 images in the high 700's. I think public safety cannot get into the 900 band. It is more for business, PUDs (utilities) and pagers.
You guys are hearing images from the front end of your scanners being overloaded. 940-960mhz is all point-to-point microwave links, and 935-940 is business trunking or conventional.