Being one of the so called "victims" of this issue I can easily tell you that the court has ordered Nakheel construction to pay back all buyers the money that had been paid for projects that have NOT started construction yet! If you have paid for any property and the construction has begun then you are simply allowed to NOT pay your installments until the end of the project.
This means that if your apartment or villa has yet to begin construction you are eligible to get a full refund from the company. Otherwise you are simply allowed to NOT pay until your building is done.
I know this for a fact as we had both situations in my family. We bought 3 apartments and we got a full refund since the construction hadn't even started yet, and we have 2 villas that had started but were on hold and we simply do not pay until the end of the construction.
This seems very unfair I agree but seeing as how most of these construction companies are governmental and not private it is the best they could do.
This issue is not in UAE only so you cannot blame the laws here. There are MANY projects world wide that get scrapped for a variety of reasons and are dealt with accordingly.
So again if your house is in the process of being built you have the right to avoid paying any further installments until the end of the project, however if the project has yet to be started (and by this I mean even pre building and making foundations) you are legally allowed to take this case to court and get a full refund.
As far as owing the bank 50mil goes, well they do not give personal loans to that extreme anymore, what they do is they will pay your installments and you will pay the bank :)