Grrr! effing anchor. alright. I will try to keep the rant in check. This is a great style, simple, easy to brew and super drinkable. The only reason northern brewer is 'definitive' is because, until recently anchor was the only one still making this style commercially. I agree that if you are going to enter in comps you probably need to use at least some NB but if you are drinking for yourself branch out! I have made cali common with cascade to great effect. a lovely beer. pretty similar recipe to mtnandy actually 9.25 pale malt .75 c60 but with NZ cascade. I have been planning one useing a hop called ivanhoe which is an heirloom variety that has recently been re-discovered here in northern california. While cascade might be a bit out of style it is really good but any cluster type hop would work well (ivanhoe is a cluster).
The thing to remember with this style is that it was brewed with local ingredients at a time when brewing technology was still fairly low. historically there is some evidence that it was brewed with at least part domestic 6 row. If you look at the temps in the SF bay area they average in the 60's-70's and stick pretty close to that average year round. at the time this style was popular refridgeration was only available via big ice blocks or expensive chemical (ammonia based) commercial refridgeration so they were fermented warmish. The yeast was most likely lager yeast brought over to the new world by german immigrants and fermented warm due to the lack of refridgeration.
all this being said, my only real point is to not get stuck in the 'must have NB' mindset. It's true that to win a comp you would probably have to use them but to make a wonderful beer you do not. try any kin dof hop. try citra, or fuggles. (fuggles might actually be really good come to think of it) but keep the grain bill super simple.