Each motor mount is made up of two right angle brackets with a rubber cushion between them. One is bolted to the frame and the other is bolted to the bell housing and sits on top of the one on the frame. There is a bolt between the rubber cushion that holds everything together so under enough torque one side does not lift up too much.
The odds of these brackets breaking is slim so the bolts coming loose is a more likely option. Even if one side broke, the other would hold the engine up for a while. Doubt you would hear or feel this movement on a DP.
Here are some pictures of a Cummins ISC bell housing
mounts but they would be pointing down when bolted to the bell housing. The mounts on my ISL are much heavier and not of cast iron and yes I went and checked mine... not something I would normally do.
