It's from their clients - presumably when SISU walk away, they will be taking their clients' money with them to invest in other projects.
Unless you know something we don't, SISU don't get any share of "income streams" ... they really are on a hidiing to nothing, they tried Plan A and that failed, so they kicked out Uncle Ray and tried to trade out of it with an austerity drive - failed and they landed in L1. Now it's all about Plan C which is the Ricoh and the land around it, if they can pick that up for a song and sell it on, they still have a chance of keeping their shirts and their credibility. If ACL can stare them down, there is no Plan D and they will have to accept pretty much any offer to do a deal on the debt and walk away.