I never realised the XPS was through a NC contact.
It'll depend on the spec. Some will be designed so the contact closes regardless, others will hold it open. On larger contactors, you can normally wedge a small screwdriver in and close a single contact, which would then let you see if the NC contact opens or not, however smaller contactors are usually far more enclosed.

Having said that, at the currents you're working with, the contactor should never weld shut, so I wouldn't worry about it. Even if it was to stick and maintain full power, the power being maintained should not be the sole reason if the machine wasn't to stop during an e-stop.