Rogue Shadows
Banned
snip
The thing is, Russia has no border with France despite being at war with her, and no way to threaten French assets without moving overland. So Alexander II's only real avenue of attack is through either Prussia (and a bit of Hanover) or Austria, then either Switzerland or Italy.
Given that the Prussian route is shorter and the Germans really don't like the French, a Prusso-Russian alliance seems likely, especially since Prussia is going to have to deal with France sooner or later, and an opportunity like this - getting ~75 million extra people behind you - doesn't come along every day.
Add in what I still feel is the distinct possibility of Austria joining out of spite towards France and fear of Prussian and Russian revanchism, and hoping to share in the influence (imagine how strong Austria will be in Italy if there's no France strong enough to curb her influence! At least that's what Alexander II and whoever the Prussian king is (Wilhelm?) will say)