I went through this several years ago on my 2003 V70. As I recall I had to turn the key to position I or II in order to allow the trans lock cable to be (easily) disconnected. But if you can’t turn the key…….?
You may have to try removing the flat plate from the lock assembly and shake out any broken fragments from inside before you can get the key to turn. Actually, if you were to do that, it might just solve your whole problem, cancelling the need for a locksmith.

I have no idea what might be involved with disconnecting the cable at the shifter, allowing slack in the cable so that it can be removed from the lock assembly. I think I’d go for removing the flat plate at this point. It’s going to have to be opened up anyway either by you or someone else. You do need to leave enough of the aluminum casting around the edge of the plate in order to peen it back down around the edge of the plate when reassembling.