There IS mention of having the same tires all around in your owners manual and it also tells you not to drive more than a few short miles (like 40) on your included spacesaver spare, keeping speeds low also ......or else!
Believe it or not, driving just over those few miles on your spare tire will blow out that angle gear as incredible as that in itself may seem.
I know about the tech-net note BUT VCOA NEVER tells dealer staff anywhere that it's their job to forward any SBs or tech net notes to any customers, that's just pure BS, whoever told you that is dead wrong.
Now, at 500 miles since the first angle gear was replaced and being that they didn't notice the tires the first time (which they should have as that's why the part failed, especially being that they NOW even now admit to knowing about the tech-net note), if they don't "parts warranty" the newly failed part completely (labor included, no charge to you) it's then time to first call Volvos customer service #, then a lawyer if that doesn't help. You WILL need to get 4 new matching tires as that's obvious but they should have caught that in the begining, not after yet another angle failed. The AWD XCs always need 4 matching tires all the way around, not a mismatch ever.
It's because of this very BS situation of a very poorly designed, add-on, weak AWD system that the XCs are on a "don't buy" list at consumer reports. Anytime you need one or two new tires, you MUST replace ALL 4 at the same time AND they must all be the same type, model, size tire all around, no exceptions. If you ever need that included space saver spare, don't drive on it more than a few miles, VERY few like maybe 10 miles and stay off the freeway. Be very carefull using that POS thing as it too has the wrong running diameter even though Volvo (NOT the dealer) put it in your car.
The whole situation STILL amazes me to be quite honest.