Is it possible to transfer "likes" from Facebook to Google+, or vice versa? In order to do this, I'd need a list of corresponding pages on both Facebook and Google+, so that if I "liked" the page about Google on Facebook, it would be transferred to Google+.
Facebook and Google Plus are two separate social networks. For practicality's sake, a "Like" action on Facebook is the same as a "+1" action on Google+. You could like a particular page that is present on Facebook at facebook.com/page1 but that page doesn't exist on google plus making it impossible to duplicate the action from one network to the other, at least automatically. If you want to replicate actions, you could try and create a separate application on each network (a facebook app and a google+ app that work individually and both apps could plausibly connect to a common dataspace).
No. Even though the idea is kind of impractical, it's literally impossible as Google+ API doesn't allow +1 ing.
Not possible. Google Plus and Facebook are totally different applications and more over they are competitors. Neither Google nor facebook is going to come up with an api that will allow you to do that.