Yeah, I have seen data showing biodiesel to have almost an order of magnitude better lubricity than regular #2, so they are full of crap on that issue. I have talked to countless older mechanics who try to find anything they can wrong with any new fuel, so being dismissive of biodiesel as bad for the IP wouldn't surprise me. My dad was the same way when ethanol blends started showing up in Iowa (although he did have a point in the case of older carburated engines with the foam floats that would dissolve in ethanol). It took him years to admit ethanol was okay even for modern fuel-injected cars.
As far as what really did cause the wear in that IP on the bus, it is hard to tell. Could have been a bad batch of fuel (bio or petrodiesel) that had a lot of water in it. Could have had massive fuel filter failure. Could have been any number of things, but I would bet the farm it was not the simple fact of using biodiesel.

On edit: I just looked at the data provided above and even that shows biodiesel to have much better lubricity. The scar number being smaller means there was less wear, therefore better lubricity. The friction number was about half as well. In those two instances, smaller numbers are better.

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Keep everything as simple as possible-but no simpler--Albert Einstein