I haven't dug into it, but coming from an RF background I'd bet the signals differ enough (frequency, pulse width, pulse duration, scan type, etc) that a filter could be applied.
Grocery store motion sensors for automatic doors seem to blast constantly like police sources so those are tough (but primarily X band, which is getting rare for police depending on the area, so ignoring X is an option). But car safety systems are bursty (maybe to reduce power consumption / heat dissipation?), so good detectors are able to filter based on such pulse signatures, basically just delaying the determination to alert by about half a second to see how constant the source is.