Thylo, you might as well forget about the intervals and just get some miles into those legs. The intervals will only make you want to stay off the bike. They're not really necessary for enduro style events anyway where the emphasis is on tempo.

4 man team? That means three hours on the bike which is about 90 kays in road miles and (I think) about 60 kays of up and down hill MTB crud. You could do that with no training at all but you probably wouldn't walk for about a week afterwards

So there you have it. Start with an hour a day (28-30 kays of easy, flat road miles) then GRADUALLY increase the weekend mileage to four hours of flat/undulating stuff per day and put in some hills during the shorter rides during the week. On the hilly stuff you don't need to bust a valve, just concentrate on tempo. If you are worried about strength then climb seated (or alternate between seated and standing each repeat).

And make sure you take Monday and Friday off. You'll need mucho recovery time so your body can regenrate the stuff you'll be breaking as you increase the load.

Have fun

PS. Did I mention that you should increase the time and the effort GRADUALLY?