Hi,
I did the TR24 last year (doing it this year also) in a team of 5 and loved it.
I done 4 laps and will be looking to do 4-5 this year. I didn't change my training at all to be honest. (LSR on Sunday, Harriers speed work on Tuesday and tempo on Thursday) and found it absolutly fine.
I found the toughest thing was the tiredness. I done a lap somewhere round 1am and was knackered but the rest were fine.
I can't comment on comparing it to 50k ultra training, but I don't think you need that kind of training if your only planning on running 4 or 5 laps. Remember they are only 10k laps and you should get a few hours rest inbetween; depending on how fast your mates are.
if you only run on roads though, I would suggest getting some trail shoes and going off road to get used to it.
But then again, i'm doing the Lightning 12 hour as a solo (fool) and still haven't changed my training; so what do I know.

Whatever happens, I can pretty much guarantee you'll have a cracking time.
Mick