Let's correct the numbers. Today there are 9.5k employees, in the future up to 13k. That is a 37% increase (according to the video at 9:20 its 40% ). Then at 16:37 Jobs claims that they will only be increasing the employment by 20%.
He also speaks at some point (towards the end) about a series of buses used to transport workers. Hence the increase in use of private transportation will probably not be at around 40%, but probably around 20%. (Buses do cause some traffic, but much less that cars).
Because this is a very large project I am pretty sure they have thought about the traffic issues, and wouldn't insist on building there if there would produce too much new traffic. Also the council would object to the idea if it would cause much traffic congestion.
Hence, I said that you are wrong about there being congestion due to the new influx of workers. If the 20% figure is correct and that they have thought about possible traffic issues, then there might not be a significant increase in congestion. However it will probably be noticeable. (Notice the difference between _noticeable_ and _significant_).
I live in Eastern Europe, and have very limited knowledge of the the transportation routes in Cupertino. I would very much enjoy the opinion of someone knowledgeable.
> Also the council would object to the idea if it would cause much traffic congestion
The thing is, they're not up to that stage yet. They haven't even seen the plans. The question that guy asked was objecting to the idea, to the extent possible at this early stage.
BTW: When starting off replies with "You are wrong", it's best to be sure that (a) it is an issue that one can be clearly right or wrong about (e.g. arithmetic); and (b) you are correct. In fact, given (a) and (b), it is better to not even say that, and shorten it to simply present the correct answer: http://ycombinator.com/newsguidelines.html