what car (if any) is 'formula isi' based on?

i'm assuming its a specific car just because eg gsc seems to base their models heavily on one specific car from the period (312t, MP4/4, etc)

 

It's a generic Formula 1 2012 specs, car.

 

It was made around the same time as Marussia MR-01, so they might share some things. Although Marussia physics files are encrypted and the FISI files are not, so it probably does not contain sensitive data from the Marussia. You can view some physics details about it from this page.