St. Petersburg
The Tsarist Government found itself in a difficult position; Austria's expansion was happening too fast, and they had to find a way to contain it.
However, the Russian-Austrian Alliance could not be broken. Austria was the Tsarist Government's only significant ally on the European Continent, and they absolutely could not afford to lose them.
Currently, Austria had not expanded beyond the stipulations of the treaty, so they couldn't even find an excuse to intervene.
This had nothing to do with credibility; as long as it was in their interest, the Tsarist Government didn't care about betraying an ally.
Clearly, the current interests were not sufficient for the Tsar to betray an ally. Even if England and France abandoned the Ottoman Empire, the Tsarist Government would not likely tear up the Russian-Austrian treaty.