First: assembling, justifying and building these claims take about a year. You're talking hundreds of pages mostly in annexes. I prepared such for a > 1B PPP.
Second: The owner has to recruit an expert team to rebuff the portions of the claims that may not be directly related to COVID. The expert team has to go through hundreds of pages and then prepare their report. Another year or so.
Second: the claims and both positions are submitted to the dispute adjudication board (DAB) who has to make a determination. The DAB process for such claims also takes a few months easily
Owners facing such claims are vulnerable because the private partner will likely add everything and they have to defend themselves.
The DAB will recommend a settlement figure. None of tne two parties will necessarily be happy so we move to arbitration. That's another delay of about a year.
and if both don't like the settlement we go to the courts.