Correct. You definately can't. I was burned by this. Check out the thread I started
https://www.gtplanet.net/forum/showthread.php?t=139195. I spent over 8.5 hours of driving time alone over a period of two days to buy an F2007 for $12,500,000 that I can't use in any race, except a "specifically F1" restricted race made online, Practice, and Photo Travel.
The race car for the race you are refering to can be purchased in the "Used Car Lot". I seen the car there about 5-6 game days after I purchased the F2007. It costs around 4,500,000.
VDOP