Quite possibly they do have the copyright. And quite likely it is the Victory-class - after all, AoG did do most of the ships we saw in Babylon 5, from Omegas to WhiteStars. Only a few show-civilians were not miniaturized by AoG... and what else have fans been crying most about... (Though it could of course also be EF-1, another mini AoG never got around to do. Or the Icarus, another non-background ship AoG never did. Blue Star - same. Hell, if they wanted to they could even make a Jumpgate mini, complete with yellow & blue plastic "vortex". But since a Victory would probably sell best I'd think they'd start with that one...)
Now, if Mongoose were to take up the mini line where AoG left it, and slowly do all the minis they never got around to do, or didn't get the license for, I'd be really happy.
Especially if they were to do all those minis that are usually overlooked in wargames, but so common in Roleplaying encounters - civilian freighters, small transports, shuttles, etc. - and scaled to fit in with the AoG-made B5W ships, most of which are still available from some sources.
I would be even more happy if they did revive the old AoG mini lines too some day (when all still existing stocks of AoG minis have disappeared). Maybe even improve some of the not-so-good ones... (hollow-bottom minis like the Avenger Carrier - an extra bottom plate would be easy to sculpt; or oversized ones like the Markab Shafab - though that could also be fixed by making it a battleship-sized vessel in their incarnation...) even if they would charge more for them... or if they did it on a pre-order base (as in - "We'll do that mini as soon as we get 200 binding orders for it, as then our production costs would be covered"; something like that exists with another company IIRC.)
Similar goes for the B5 character minis by the late company Harlequin - I'd like to see Mongoose do something similar or maybe even pick up the line if that were possible (dunno if the molds were all destroyed when Harlequin lost the license in their transition to Icon minis, or if a master still exists... or enough samples to recreate them... of if the legal entanglements can be untangled without too much hasslöe for Mongoose... well, time might tell.)
Cardboard... Yuck :?
OK, cardboard stuff is OK to include in a boxed game, as it allows new players get into it without having to spend a lot - "just buy the box, give it a try, and see if you like it"; whereas needing scores of miniatures does rise the price tag quite a bit, and thus is accepatable only for games that are well established and have a large following stupid enough to pay exaggerated prices for the miniatures they need...
But for those who stay with a game, and can afford to spare a bit of extra mones from time to time, miniatures are the way to go (most slowly start building their mini forces even before a sudden gust of wind wipes out a game they have played for hours...). Very nice for promotion of the game too, if you can do demos (and put pix into the 'net) with well-painted minis - the eye usually is the first sense to spot a new game after all, especially in our visual-oriented times.
So while I dislike cardboard, I have to say it'd be smart of Mongoose to do both - mini only games have a much harder start then cardboard-including games, and cardboard-only games have a lot less appeal and expansion possibilitis then games with miniatures avaiable. So if you do something, do both, cardboard now, metal minis later. It worked for others before...