I don't understand Rebuild very well, but I'm quite sure about how Rebuild like the different alternate VPs.
IN GENERAL: Rebuild is good in accelarating the game. It's able to beat engines, not because it's strong, but because it's fast. Some strategies might be able to get 4 Provinces in like 15 turns, but Rebuild do that AND trash 4 Duchies and maybe some Estates, which is a big deal, because if you take the same example with 5 Provinces, an engine player isn't able to catch up any more (3 Provinces, 3 Duchies isn't enough), but he could if there would still be the duchies. That's where alternate VP get important.
For an engine player, Alternate VP is great to catch up a BM-Player. The same for the Rebuild vs. Non-Rebuild-Player. But let's look at the individual cards:
Tunnel: Rebuild-Tunnel is insanely fast. Just get golds from 4-5 Tunnels about 3 turns and your deck has plenty of golds. Now you just buy Provinces and Duchies while getting some more golds and rebuilding the duchies into provinces. Very powerful combo.
Feodum: Feodum is not such a great Rebuild supporter like Tunnel, but if you take the risk of a longer game by taking an extra step via feodum, you have plenty of silvers to grab the duchies more quickly (and maybe even buying provinces)
Gardens/Silk Roads: Theres the first alternate path to victory. These cards will help Rebuild almost nothing, but they are generating more points to catch up. Gardens are not that great, because if you're not running a rush or slog deck, they are not worth much and the Rebuilder can destroy them (ok, it takes longer time for him but...) without fearing that you can change your strategy quickly. But Silk Road is great to catch up as late VP-Cards, when the big VPs are gone, to be able to catch up a Rebuilder with 5-6 Provinces.
Fairgrounds: Fairgrounds is similar to Silk Roads. It doesn't help much for the Rebuilder, but they could be an additional province pile for you. The Rebuilder can destroy them with Duchy-->Fairgrounds-->Province, but that will slow his rebuilding down a lot, and now you'll just buy Provinces instead of Fairgrounds, so you will always profit therefrom.
Colonies: Colonies generate massive extra VP. In our example of the 5 Province-Rebuilder, the engine player isn't able to catch up without gaining all remaining estates, but in case of a 5-Colonies-Rebuilder, the engine player can win with, 3 Colonies, 3 Provinces and some Duchies. Not talking about lots of extra time the Rebuilder need to rebuild these Provinces into Colonies.
Vineyards/VP-tokens: These are like the elite counters against rebuild. Rebuild cannot destroy them, only buy them itself. An engine with vineyards equal/more worth than provinces or a strong goons engine just outraces Rebuild.
Duke: I'm not sure about this. It's obviously strong with Rebuild, but also quite much extra VP for the opponent. A plus for the Rebuilder is maybe that he's able to rebuild dukes or duchies into provinces if he lost the split.
The other VPs (Great Hall, Island, Harem, Nobles) don't have much impact on a Rebuild game. But an interesting case can appear, if there are any $3 or $4 cost VPs AND any $5 or $6 cost alternate VPs, because the duchy split loses importance, because you can jump it over (e.g Great Hall -> Harem).
In that case, Great Hall and Harem are quite helpful (more helpful than Tunnel, Island, Fairgrounds or Nobles), because they don't hurt much in the deck if your drawing them