Can't help you with the insurance question per se but my guess is you are correct that if you didn't carry additional insurance via your own policy then you may have nothing left but a civil suit against the owner over and beyond what his insurance pays.... Assuming he was at fault and I know you said you were t-boned but you didn't specify who was at fault.
They have assumed complete fault and boy was it. My own insurance will not insure mods and to be honest that is her companey's concern not mine. Lawsuit seems pointless given her car and it's condition; no money there.