Greg,
I was surprised that the website (www.bbc.co.uk/news) used the word tallow - unless it was a simplified way of conveying an idea of the consistency of the used oil that was intended for future use.

I also picked up on the fact that the bio-diesel was being heated prior to injection. If they find it necessary to do this with a big diesel in an engine room which would probably be at a reasonably high temperature, then it doesn't bode well for using the stuff in a small model engine ! Like you I greatly doubt the feasability of a single fuel component which also acts as the lubricant... the two requirements are somewhat incompatible.

Reg