Well, let's just confirm what the "Tome of All Knowledge, v2" says on this issue,....
:hmmm: hum-humming,....rum-rummaging. It's around here somewhere,...ahah!
<flip-flip-flip> A10.31,....A10.31,...uhuh, here it is.
<huzub-zub-zub-zub-zub> bloody exceptions,....<huzub-zub-zub>.
<Ahem> Well then, that does seem pretty clear then, doesn't it. I quote:
" A10.31 CASUALTY MC:If an unbroken Personnel unit rolls an Original 12 during an MC, it suffers Casualty Reduction and is broken (or eliminated if not subject to breaking) [EXC: <snip bit about heroes, berserk SMC and Japanese] -after any unit Replacement which may also be required by ELR failure (19.13). <snip part about broken units>."
Bold italics are mine.
That, I suppose, is that. Deploy into two HS (for ELR failure)and use RS for determining who is CR'd. Rule is not specific about the SW but I suspect RS to determine possession.