Not going to let a good post go to waste, so:
Having played the game since it came out, I was a bit bored with it and sometime ago I decided to create a new user and start it again. Little did I know the tunes didn't come with the new user, but oh well, I started completely afresh.
In doing so, I've had to do the annoying licenses (most are great, but some are horrible) and the infamous Senna challenges. Also, and equally annoying, are the Red Bull races and championships, especially when I have a DS3 controller.
I have taken a liking to the course maker and was fiddling around with a downloaded track called Formez Les Rangs, by Baka5D, which I had raced a while before. After playing around with it, I decided to get ahead a little further in the game and try out the X2014 Junior races. After the 2nd race I had to get back to work, so I suspended the race, saved and got back to it later.
When I restarted the race, instead of going to Grand Valley East track, the race started in the custom track I played before. I figured it was a bug and decided to start the race. Lo and behold, the race actually took part in the custom track!
Apologies for the crappy video and the shady driving (I wasn't an expert on the X2014 Jr.'s handling) and the rest of the AI were pretty amazed by the track as well. I only put one lap on the video, since it's a fairly long one and the phone camera could only hold for so long before running out of space.
For the following race (which should've been Rome), I tried suspending again and exiting the game. When I logged in again, there it was, the same Formez Les Rangs custom track, counting as Race 4 of the championship. I did it again, and for race 5 I got the one I was supposed to.