Redirected folder - First time setup for user with multiple local profiles on multiple machines. New files merge, ignored?

This is all running in a 2008 AD with Win 7 client workstations.

Have a department that is manned 24/7 by multiple users who roam between three different computers.  As such each user has their own local profile on each of the machines.

When redirected folders is implemented the files are copied to the network location when JoeUser logs on to Computer1 the files are copied up to specified location.

So what happens to any possible different files on Computer2 when JoeUser logs in.  Are different files found in the local My Documents of the second computer ignored?  Copied?

Hope that makes sense.  Thanks for your help.