Because Mirror's Edge uses a better game engine than Blockland. Motion Blur can not be done as an Add-On. It would have to be done in the engine. As Flubb said, I don't think Torque even supports something like that. If it does, he would need more of a reason to add it than "It'd be nice." Like everything impossible normally, I'm sure people will offer alternatives. The thing is, no one goes through with the alternatives because they are usually hacky or not enough like what was asked. To release the such gets only ridicule, so no one has the nerve to do it. I'm sorry.
That was video editing in the videos you saw. You can take blurry screenshots because of the process that makes them, which in no way can function live efficiently.
Edit: http://www.garagegames.com/community/forums/viewthread/67530For Torque Game Engine ADVANCED. I doubt it can be applied to our regular version, but if so, still needs to be implemented by Badspot.
