I agree Russia is positioning itself, yet I still believe at some level this is a genuine effort at global cooperation *ducks*. And there is already defense against cruise missiles (Patriot missiles, etc.), so is it not plausible that cooperation can protect the involved nations from cruise missiles as well? It would be trickier because of range issues, but still plausible.
And yes, one of the motivations is definitely the lucrative contracts. However, Russia would not agree to this unless some political gain is won. A couple multimillion dollar contracts are not enough to sway the foreign policy of such a large nation.