Not all champagne yeasts are killer strains, but even if the one you used is, the fact that it was pitched into a high alcohol environment without a source of energy might have killed it. At the least, it'll be inactive, so shouldn't affect other yeasts in there.
If I can suggest another approach... it's also pretty tough for a starter, even a pretty big one, to get going when the ABV is already up around 12%. If it were my batch, I'd get another pitch of WLP099 and make a smaller beer with it (5-6% ABV) and let it ferment out. Rack it off the yeast cake, and dump the barley wine onto it.
You MIGHT consider oxygenating it. I'm not saying you should, but I would think really hard about doing it. WLP099 should be able to get up to 15-16% without extreme measures. Getting it north of 20% ABV requires step feeding and heavy oxygenation during fermentation. I'm not sure what would happen if you oxygenate at this point, whether it would oxidize the beer or if the yeast would scrub it. Maybe see if it starts fermenting first? Just thinking out loud. Either way, it'll proceed very slowly, but it should scrub off quite a few gravity points.
Another thing to consider is brett. Brux can survive up to 15-16% ABV, and could probably handle direct pitching. It'll also take awhile, and I wouldn't consider bottling it for at least 6 months if you got that route. The wyeast brux strain would probably be awesome in a barley wine, though.