I believe the SnapMirror connection shouldn't be an issue as you're taking the entire volume over along with the baseline snapshot + other snapshots. You'll want to make sure that the 270 is at the same or later ONTap version however (regular volume SnapMirror requirements).
For SME/SMSQL, you'll want to do something like....
- stop SQL/Exchange/etc.
- disconnect the LUNs in SnapDrive and remove them from the system
- migrate the shelf to the new NetApp
- make the LUNs available to the SQL/Exchange server from the new NetApp (igroup setup, LUN from an existing file -- this part I'm not quite sure of -- can anyone correct me here?)
- using SnapDrive, connect to an existing LUN on the SQL/Exchange server making sure to use the same drive letters
I would model some of this if you can.....you don't have to move the shelf but could do some of it with a new volume/LUN/SnapDrive and testing the steps.