If the domain holder has requested to deregister the domain name and then change registrars during the deactivation period, the earlier deregistration request will be cancelled. (In EPP, the parameter ClientDelete will be set to "0" and the set ClienDeleteDate as well as the ClientDeactivationDate are removed. )
If the domain holder wants to deregister the domain name this has to be requested again under the new registrar. This way, the current registrar will also have the basis for the deregistration.