Evidence for Compensation Event Quotations

A compensation event quotation has been issued to the client under NEC4 Option A contract. The quotation includes elements of subcontractor involvement and a quotation has been provided to support. However there are elements where the subcontractor has subcontracted and the client is asking for not only subcontractor quotations but sub subcontractor quotations.

My question is how far can a client ask a contractor to provide quotations to support a CE with regards to subcontractors and their subcontractors? How far down the chain is a contractor required to go to provide evidence?