Its tough, but i did it. Unless you are going to hit someone you really dont need to slow down for many turns. The buses dont go fast enough for it to be a problem. You can get to 11th at the first turn but cutting in very close to the cone (dont hit it!) and downshifting to slide a little. Sneak into 11th and start drafting the bus in front of you. Theres an easy left where you can pass on the inside and take one more place, then get as close to the tires on the right as possible and you'll be able to grab a few more spots before you hit the 2nd straight.
The next turn is a hard left into an easy 180º right. Be careful on the left as its easy to hit a cone, then cut close to the inside of the right. When you get out of that turn you should be directly behind the blue and teal buses. You wont be able to pass them for a while so draft as best as you can until you get to the hard left at the complete other end of the track. Take that turn really wide and stay to the inside as you exit. You should be able to stay at speed and sneak right by if you are careful enough to not bump into them. If you are too close just back off a little, as long as you pass the blue buses at this turn you are doing great. Just be careful.
The next is a hard left that takes you back to the starting line. If you got ahead of the blue and teal bus there will be a bit of congestion there. Stay close to the inside but be careful you dont hit the grass too much. You should be able to get 5th or 6th before the 2nd lap starts. Follow the same lines as before and watch your corners for a chance to pass on the inside. I got to 1st at the last long straight, but the dark green bus in front is a little violent, so screw the line and do whatever it takes to stay away from him. Take both last lefts carefully and you'll grab first.
Its tough, but possible when you learn the track. I havent tried the Lotus challenge yet because i've been working on licenses, but i assume its roughly the same process just much faster.