Well, I have a passing familiarity with brushless motors - mostly dealing with computer fans and the bigger brother, ECM blower motors. I'm sure some of our other electronics guys will be more helpful - but for starters do you have any more information about these motors? Part numbers on anything (circuit boards, etc), OEM manufacturer, etc? This information would give more insight into how these particular motors are built.
Off the top of my head, brushless motors seem pretty durable in design. With the caveat of not having experience with your particular product, I would expect impact related forces to cause mechanical issues with bent and binding parts more then electrical issues.