I would imagine that you could remove the sensors without removing the camera's housing to preserve the waterproofing. But I'd be surprised if a company that doesn't allow cellphones with cameras would allow a smartphone that has no camera. Especially an android because they can act as a flash drive just as easily as any thumb drive.
As for a tear down, I have no idea. I did a quick Google search and couldn't find anything for the Xperia Active. But I'd imagine that it'd be similar to one of the other Xperias. XDA groups it with the Xperia Mini, so maybe looking for that would yield better results?