The modding team ACFL have publicly released their F1 2015 mod for Assetto Corsa.
This mod features all 20 cars from the 2015 season along with the 10 teams that compete full time.
All the cars feature the same physics but each one has its own car model so it can be used for league racing.
The current version of this mod is 3.2 and it can be found via – THIS LINK
They also have a very nice trailer showing the cars at Imola.
The ACFL website and forums can be found – HERE