I wouldn't recommend it. In my other car, I hard wired a Whistler XTR690 radar detector to my autodimming mirror and at first everything seems fine. The radar would turn on when I started the car and powered off when I turned off the ignition. Everything seem to be working as I was getting the warnings and flashes. Then I started noticing the radar started loosing its user programmed settings. I thought my unit was bad and sent it to Whistler for repair. I actually had a Whistler repair technician contacted me to discuss my radar. He said he ran a battery of tests and found no issues. He asked where I was getting power and I told him from the rearview mirror. He tells me its difficult to tell how much current the thin wire on the rearview mirror can supply. When I got it back, I hard wired it to the fuse box and no more problem.
There are 2 questions you need to answer before wiring to the rearview mirror. 1) How much current (not voltage) will your radar detector require? 2) How much current (not voltage) the factory wiring on the rearview mirror can supply? Without using a multimeter to test amperage on both sides, you will not know. Also the biggest problem is what I ran into which is the radar powered up but the circuits inside wasn't getting enough juice to operate optimally meaning the radar antenna probably wasn't working as per spec as it should. The radar probably wasn't detecting the radar traps as well as it should.
I know my story applied to a different vehicle than the Ody but until you can truly answer the above question 1) and 2), you will not know if your radar is getting adequate current source to operate properly.