Indeed, nuclear1 is simply surmising that the Bastion was in Capella beforehand, and moved out for the modifications in Vega, because it would have been in danger in Capella (as Singh mentioned), and the Meson Production Facilities were based in Vega (I think...), hence making that system the ideal place for the modifications to take place. There's absolutely no evidence to contradict (or support for that matter) that the Bastion wasn't in Capella, and thus it falls within artistic license..
...on a side note, nuclear1, why didn't you use the seperate GTD Bastion Orion model, completele with nameplate...?