Yeah, I think 1900 is way too late for the other powers to leave Russia do what it wants, and it is also too early for Russia to find an excuse to do that, the Balkans had been quiet only for the last 15 years at this point and there isn't an Anglo-Russian Convention/Entente yet to neutralise the threat of British intervention.
If, however, Russia does somehow manage to pull this, I believe it would treat AH and the Ottomans very differently. I can see them aspiring to force a San Stafano II of sorts to the Ottomans. The odd thing here is that the only remaining Russo-Turkish border is now in the East, in Caucasus. It would be a very bloody and very messy affair. As a result, Russians couldn't have made large gains and they would have no viable way to reach Constantinople (I'm guessing a Russian fleet in the Dardanelles is a no go for fear of the English). Thus, the only possible gain for them is the westwards expansion of the caucasian-anatolian border. The biq question here is what happens with/to the Armenians. Under the right circumstances, they could even get an autonomous state under either Russian protection or Ottoman suzerainty.
As for AH, it depends on what is Russia's long term thinking. If they want to not make them hatred enemies of theirs, they would only get Ruthenian strongly-majority areas of Galicia while giving something (territory, monetary compensation, free had in Serbia/Balkans) back. Otherwise, they take most or all of Galicia and Austria becomes Germany's puppet earlier.