Why? Intelligence service from both countries have been talking about cooperating deeper since the Boston Marathon bombing. This is an official step in that direction. Makes perfect sense that they would help each other. Russia has no love at ALL for radical Islam.
The Russians did everything they could to warn us about the Boston bombers - more than once. Maybe more than two or three times... And we didn’t bother to pay attention to what they said. The problem isn’t that we need to ‘share’ it’s that we need too open up our minds and listen to warnings.