It's a blend of MadCapellans Objective raids (really quite good, IMO), TRO entries, and my memory.
Not 100% sure on Achernar mechs, but fairly sure that at one time, all those mechs were made there. Feel 100% sure about the lines at Corean. Although I don't know if the Jihad destroyed any mechlines at either factory.
But between all those mech lines, the battle armor lines, and the Aerospace lines, New Avalon is at least 'indispensable' as far as planets go. Every month that the Combine is in possession of those lines they can at least add a few mechs to the DCMS and deny them to the FedSuns.
I'm pretty sure most Draconis mechwarriors wouldn't pilot a Valkyrie or an Enforcer, because they are such iconic FedSuns mechs. I wouldn't be surprised if those factories get demolished.
But Centurion Omnis, BlackHawk KUs, and Vulpes mechs? You can bet your bottom dollar those would find welcome homes in the DCMS.