I would guess that the belt is GoodYear but am not too sure about anything else. Do Goodyear sell the complete kits or do you have to buy the tensioners seperatly?
I think i can live with it for now as it's not old or over due. As it stands the belt is 18 months old with 22k miles. I'll probably change it before the end of summer just for piece of mind though!
While having an original GM kit is reassuring, I don't not see a problem with a kit from reputable manufacturers such as SKF (yes they make cambelt kits), Gates, Conti, etc.
So I see where you are coming from... if Goodyear made the whole kit, then there is a better chance that they used good-quality tensioner and idlers (though they probably wouldn't make them themselves). On the other hand if some little-known company was putting cambelt kits together and were using the Goodyear belt, there is no way of knowing if they also invested in good tensioner and rollers...
If you can take-off the cambelt cover you will be able to take a closer look at the tensioner and see if there are any marking on it, such as SKF or possibly even GM....
Having said that, the golden rule regarding cambelt tensioner is 'if in doubt, there is no doubt' (it's a modern rephrase for 'better safe than sorry'...).