rman is you friend especially with ASM most of the time there it is your only friend.
so basically it comes down to put the correct DB_UNIQUE_NAME bounce the instance put it in mount ...
and of course make sure that you put the device channel disk in rman correctly in our case
CONFIGURE CHANNEL DEVICE TYPE DISK FORMAT '+DATADG1'
this is handled by the db_recovery_file_dest parameter or can be controlled
with backup as copy ... format '+DATADG1' clause
so here goes :
rman target /
backup as copy datafile 652 ;
after this finishes
switch datafile to copy ;
this is an example to do it on datafile level ofcourse you can do it on db level as well with
backup as copy database
you can delete the old files in old asm directory.