Nope - but if they want ACL free and clear of debt that's what they'd need to pay. They could, in theory, buy ACL in entirety for £13-14 million, but ACL would still have to service the mortgage.
SISU's plan (Fisher's Roadmap) was to clear the mortgage, because that's the prime driver of the rent that the club pays. No mortgage, much lower rent. If they wanted to follow that plan, then they need to find around £20m - and that still leaves CCC as 50% holders of ACL, as did the original roadmap.
It wasn't a bad plan, the roadmap, imho. It would have given the club most of what it wants. The problem was the way that SISU tried to negotiate - the rent strike, the lack of security for Higgs, the unilateral approach to the bank, the concept of getting the bank loan at a distressed value, the absence of a proof of funding etc..
I think it's worth revisiting, but on a calmer more sensible footing - the problem is that I think SISU have now decided to take an even bigger punt on getting everything through the JR. Until that's done I can't see how the sides can start talking again.