706.1.1 Party walls. Any wall located on a lot line between adjacent buildings, which is used or adapted for joint service between the two buildings, shall be constructed as a fire wall in accordance with Section 706. Party walls shall be constructed without openings and shall create separate buildings.
Exception: Openings in a party wall separating an anchor building and a mall shall be in accordance with Section 402.7.3.1.
LOT. A portion or parcel of land considered as a unit.
LOT LINE. A line dividing one lot from another, or from a street or any public place.
and of course...
FIRE SEPARATION DISTANCE. The distance measured from the building face to one of the following:
1. To the closest interior lot line; or
I think I mentioned Party Wall a few pages back...
If you're going to the IBC for a solution the first provision (Party Wall) becomes a problem.
If staying in the IRC the last item (Fire Seperation Distance) does.
The only way to allow, IMHO, would be to eliminate the lot line.
NYS has much different Administrative provisions than most of the rest of you, so I won't opine on the idea of a waiver or variance.
The Code may not address ownership, per se, but it certainly recgnizes lot lines and Distance Seperations.
Once the lot line is eliminated, it is either a two-family with rated wall or a single family with two kitchens.
As far as the electrical supply, a service can have more than one meter attached, but a single lot can have only one service (with some limited exceptions).