The Empire moved some of its production facilities or set up new ones, but their Clantech manufacturing is very limited. They make three 'Mechs in limited numbers (Warwolf, Wulfen, Tomahawk II), one Tank (Aseir AA tank) and one Battle Armour (Black Wolf) but everything else is captured Inner Sphere facilities. Of course, given that the captured worlds include Keystone, Thermopolis and Solaris VII, that gives them an awful lot of production
The existing facilities in the OZ seem to have been mostly dismantled or scrapped, with the equipmen gone/wrecked but the physical buildings still standing. Any that survived wiuld now be in the hands of the Hells Horses