Let's see.

EM claims that Tesla will produce 5K Model 3s a month by October. He has promised that to the investors (nee stockholders). Now, he could be fudging and including Model S and X and time-traveling roadster and funny electric truck production in that, but those are just rounding errors. Call it 5K with whatever product mix.

Call it 5 weeks a month on average, no wait, make it 4 because there will be weekends and holidays, right? Or do normal work rules not apply when you're working for The World's Greatest Car Company?

So 5K/month / 4 = 1.25K/week. That's more than a few containers full, but still less than half of the normal production when NUMMI was there (10K/week) with, on the whole, poorer quality control (though they're working on that). Anyway, let's not annoy the Tesla fanboi any more than necessary. Assume it all works. That's 1.25K cars a week that will be trucked to Richmond on a freeway that's already a parking lot 18 hours a day. What could possibly go wrong? Perhaps he has produced enough of his funny electric semi tractors that it will all be done with them?

Now we need some estimate of how many cars will fit on trains to the export points (and why not Oakland for that? pointless questions...). So that would provide how many trains a week BNSF could get out of this (and that UP would be giving up - though remember UP has a record of shutting off perfectly good, paying customers just, well, because).