You can drive there as part of a larger configuration but you can't put a start grid on it, as you can only use existing grids (or the single autocross start position).
No, that new section is not opened up in this patch. It's very unfinished there, experimental and lacks barriers so you can just fall into the underworld. I don't know how far Eric will go with it in the future.
by Storm_Cloud : Question answered
Most interested to know about this.
There are also a few currently closed off roads to all configs at South City. Will they be included when opened? For example, the off ramp before the hairpin on Long - that dips down into a left hander which would be interesting in faster cars.
They are still unmovable. They are not perfect - you can still get some unrealistic collisions with them, for example if you drive into their end you will probably get a strange intersection. But if you just hit them in the side, you will just bounce off them like a wall beside a track, and if you ram them they just stop you, you don't just pass through or get flung in the air.