two ideas for you.
1) Doesn't jobo make something for cleaning out their tanks?
2) I once used amonia to clean out the residue on one of my small plastic tanks, it did a good job. I haven't noticed any problems with the tank, or my film since the cleaning, so I would suspect it is ok to use it.
ps, does this mean we are are going to be able to send our film to you for processing now?