nuget location in Xamarin Studio

After recent update to Xamarin Studio 6.2 I've updated my Xamarin.Forms project to project.json instead of packages.config.
On our CI server we use nuget restore command to restore packages before building. Thing is that nuget bundled in Mono.framework is too old (2.12) and does not support project.json. But Xamarin Studio somehow restores packages. Seems like newer nuget version is bundled somewhere inside it so I can use it to restore packages from CLI. But I can't find it. As a temporary hack I can run sudo nuget update -self to force update nuget bundled in Mono.framework but it would be nice to get back to clean solution.