Since most Luxury Vinyl Tile (LVT) manufacturer's set a maximum temperature for radiant floor heating, the system should have little to no effect on the rubber/cork backing.
Pre-attached backing can act as an insulating layer though, meaning it can prevent the radiant heating from efficiently directing heat up through the floor. Please check with the manufacturer for the r-value of the product. Look for an assembled plank with an r-value of less than 1. The lower the r-value, the better!