I don't think the railcars are carrying fermented grain, they carry grain which spills and ferments... However getting grain to ferment is somewhat tricky compared to fruit, you need the right amount of water at the right time to get it to malt and then ferment so I'm surprised there's enough of it. Just surprising, not doubting it happens.

I assume the spills are from hoppers with worn out chutes, because I would not expect open hoppers for grain transport.

Yeah, agree. The article takes "bears killed by trains each year" and then "one guy said sometimes they are drunk on spilled grain" and then interpolated for hyperbole.

No, some of them are objectively drunk on spilled grain. It happens. Railroad maintenance-of-way workers run into them sometimes.

I don't know what fraction of bears killed by trains are drunk, though. I don't know if anyone knows. At least, I have not seen any sources.

They don't need to know what a train is to run from one, they are taller and louder than them so instincts will immediately kick in telling them to run.

In evolutionary terms I don't think that there was anything that represented a danger to grizzly bears (save adult males killing cubs) so they may not have evolved behavior patterns to run from big loud things.

I think it's safe to assume that those instincts habe been dialed in long before the current state of relative danger fell into place. Fear of wiry bipeds that aren't actually that big but might carry sparkling stuff would be a far more specific, younger and thus variable fear.

But then on the other hand train speed is dangerously difficult to assess even for us humans who in theory know full well what a train is. I believe that this is because much of the perception of movement is in terms of "size-units over time", which is why a fly at walking speed appears fast whereas big ship at 25 knots appears almost stationary unless you are too close for your own good.