Oh, absolutely. I am not disputing that at all, though it's kind of weird to see the Haken guys play on the JP guitars. I haven't seen them do that since 2010; maybe Richard Henshall has, but Charlie Griffiths has been playing 8-stringed guitars since the Visions tours. By all means, they're going to need a 7-string guitar to play the 12SS, so they might just as well do it on their JP models.
What I am disputing though, is the idea that in order to play DT material, the JP model would be the 'best' to get the job done. That claim is pretty ludicrous, and untrue as well. There's tons of guitars and makes that are just as 'good' (if not better) than the JP model. I'm not saying they're bad guitars, because they most likely aren't (I've never played them), but a guitar is a guitar and lots of other 7-strings can get the job done. JP's tone comes mostly from his amps, which are Mesa/Boogie make (JP even has his own signature amp, the Mesa/Boogie JP-2C). I'm pretty sure the Haken guys use Fractal Axe-FX exclusively, which isn't even an analog amp like the M/B is (I'm not judging, merely pointing out differences).
That said, I do not think they actively thought of literally imitating Dream Theater, since they are, for the most part, using different gear to replicate DT's sound, although they are essentially a DT cover band at this point. Them using JP guitars doesn't matter one bit to me.
In other news, I just got a ticket for the show in 013 (Tilburg, the Netherlands) to see this thing myself.