There is no restriction on placing a Raider in the same sector as an XPM, BUT also the XPM is NOT by default destroyed.
What happens to the XPM is decided by the Scenario Rules. The DEFAULT rules say nothing about it, so nothing happens.
For example, in "Open Confrontation" there is a ruling on what happens when Ravager enters the same sector as the XPM.
Thanks. That's good to know. I've always played it as the XPM gets destroyed.