It wasn't for that reason that he looked at Tom. When Geary said that, Mike made no reaction although you could tell he was seething inside. I looked up the lines and found where it takes place:
Sen. GEARY: The Corleone family has done very well here in Nevada. You own, or, you control, two major hotels in Vegas -- one in Reno. The licenses were grandfathered in, so there is no problem with the gaming commission. Now, my sources tell me that -- you plan to make a move against the Tropicalla. They tell me within a week -- you're gonna move Klingman out. (This is where he looks at Tom) That's quite an expansion. However it will leave with one little technical problem. Ahh -- The license will still be in Klingman's name.
MICHAEL:Turnbull is a good man.
I'm not sure why he glances at Tom. I'm also not sure why Mike replies with "Turnbull is a good man."
I always thought that the scene is a mirror of the scene from GF1 in which the Don puts Sollozzo on notice that he's aware that Sollozzo is backed by the Tattaglias.
Sollozzo looks at Tom and says "My compliments". Tom or Tom's people had done some digging (albeit not enough) to figure out who was backing Sollozzo.
Similarly, Geary's man Turnbull had done some investigating to figure out exactly the leverage point that they could use to squeeze Michael.
With his compliment to Turnbull Michael was reluctantly acknowledging that Geary or his associates did have something on the ball. Michael's look at Tom was probably along the lines of "Why didn't you take care of this earlier" or "Didn't you know that?"
