Can s90 seats be fitted to S60

[IMAY2023]

For the LIN. 
Pull out the cover of the center console at the passenger side. You will see grey connector. 
Look for the white and light green wire. PIN 23  and PIN 11. Just put a jumper wire from pin 23 to 11. 

Amazing how much You guys have all kind of tricks here! 

I got "new" seats with heating . 

Checked all the pins / wires. I'm only missing power (Pin 1) and LIN (Pin32). Power I can wire from fusebox, but LIN? I did not fully understand that advice above? @IMAY2023 Take LIN signals from center console, from that same wire to both seats?

They have their own CCM LIN bus. (CCM is the master and the rest are the slaves). 
4/204 SEAT HEATING MODULE RIGHT SHMR  (PIN 32) you should wire it to 4/229 HUMIDITY SENSOR HUS (A2 pin of the sensor). 
4/187 SEAT HEATING MODULE LEFT SHML (PIN 32) you should wire it to 4/222 CENTER CONSOLE SWITCH MODULE CCSM  (A5 of the switch panel)