Pan gafodd Carillion eu diddymu, gofynnodd Trafnidiaeth Cymru i ARC wneud cynnig a oedd yn dangos ei bod yn parhau yn bosibl i ARC gynnig y Tendr Terfynol heb newid elfennau hanfodol ohono.  Mae’r diddymwr ers hynny wedi trafod gyda nifer o bartïon i werthu Carillion Rail ac i gadw swyddi, ac reodd yn bosibl y byddai ARC wedi gallu sicrhau y capasiti perthnasol drwy’r broses hon.  Roedd angen i ARC gyflwyno cynnig cadarn, unwaith yr oedd y diddymwr wedi gwneud ei benderfyniad, erbyn 17:00 ar 22ain Chwefror.
When Carillion entered liquidation, Transport for Wales asked ARC to provide a proposal which demonstrated that ARC could still deliver the Final Tender without changing essential elements of it.  The liquidator has since been in discussion with a number of parties to sell Carillion Rail and to secure jobs, and it was possible that through this process, ARC could have secured the relevant capability. ARC was required to present a firm proposal once the liquidator had made its decision,  by 17:00 on 22nd February.