A search on heated seats will give you lots of great info from the past 2 years. I don't have the links readily available.
In brief, the heaters are both under the seat cover (skin) as well as attached to the skin. If you want to swap your seats for recaros (from a vw that fits the tracks), and you want to put your skins on the new frames, you WILL be transferring the heater elements. Here's the problem(s): The skins from comfortline seats / cushions do not perfectly fit on recaro frames / cushions. Next, if the recaros are unheated, you need to transfer all the wiring, assuming you have the in-dash wiring and switches.
If you want the recaro skins to stay on, you will have trouble taking the heater elements out of the old seats and putting them in the recaro seats, not to mention the wiring.
If you want to mix frames, cushions, and skins, you'll have to check with Lito! He's an expert.
You can also get Volvo seat heater elements and add them to the recaros. These can wired for control from both their own on/off switches, or (with work) from the oem switches.
Lots of great info avaialble under a search. Good luck.