In new Ducatis that is connected to ECU, so tacho is electrical, but i havent NEVER heard, that any Ducatipaso.org member have done that to Paso ever.... ANYBODY? Have You changed dashboard, where is electrical tacho???? I think, if made that from coils, those new systems dont take too much power from original system, so i think, they are safe to use. Anyway its Yours risk, not mine!
Btw, my 2002 ST4S have allready electrical tacho connected to ECU. But i think, ST2 have still mechanical, like 907IE.