It's probably not a surprise that Dick's built a feed from the manor security into his gear, it's not exactly the cameras or anything but he knows when the proximity alarm has been triggered, and the fact that Tim doesn't get in touch to let him know about anything makes him wonder, so he cuts their patrol short and heads back just to check. He can always come back out later if it's a false alarm.

He arrives back just in time to see Tim gearing up, and while he tries to hard his immediate suspicion, he's definitely curious.

"Hey Timmy... you heading out somewhere...?"