Yes, the Magpul Optic Mount fits just fine around the Ruger ISB on the take-down 10/22. I just picked ISB up this weekend and installed the mount last night. It JUST fits around the barrel as it's the same size as bull barrels.
One issue I ran into was the mount sides interfered with the fore end that came with the ISB. A few passes with a utility knife in the appropriate areas allowed it to be reattached without interference.
I had also hoped to replace the stock with a Magpul backpacker stock, but the suppressed extension that appears somewhat like a lower barrel of an O/U does not extend back far enough - there was a sizable noticeable gap between the back of the suppressor and the front of the backpacker fore end. I also had interference in trying to fit this fore end and would have had to relieve the internal channel a little as well had I decided to keep it on there. In addition, the suppressor would have prevented the fore end from being stowed in the carrying position into the bottom of the buttstock.
It is rather heavy, as someone in another thread intimated - the bull barrel part appears to be steel. Other tubular integral barrels I've used have been noticeably lighter, but this was cool being a factory option, and it does feel really good and solid in the hands - it balances on the magazine with it. I've not shot it yet to comment on its accuracy and quietness. I'll try to come back and update after shooting, but reviews have indicated it's quite quiet, and the additional volume should help with that. I do have muzzle cans I can compare it with as well - one reason I got this is I wanted something different.
@Bluemonday to notify you as this is an older post - I saw it last month, but only now picked up my ISB to be able to comment on it.