No, sorry, you would have to re-mate them all or change them from float to fixed. but if you have them all fixed you can still use the explode to have them come apart, or only mate the parts that need to be for motion.
One way is to open it as part file with multiple bodies, that way it all stays together. then if you need to you can save out the seperate bodies as their own part files when needed.
This is why step, iges and parasolid imports are referred to as dumb solids. All the intelligence of the model goes away.
Just the nature of working with imported data.