1st things first: ALWAYS CARY A WATER BOTTLE / BELT / PACK!!!!! Nobody, not even the top runners in this race, should try and finish the race using the aid stations alone. Matt Carpenter always had a water bottle on him (even on the downhill), Alex Nichols had a hydration pack for his win last year. The only folks who don't carry water are the folks who think that they are somehow better than Matt. They always suffer, horribly. I've seen it year in and year out. They may finish, but they always end up in the med tent at the end and usually end up losing significant time in the last portion of the race because of their pride.
In terms of running out, A-Frame had an issue 4 years or so ago one year where one of the two water filters broke. They didn't totally run out, they just could not filter it fast enough at times.
Cirque gets it's water from a hose run down from the summit. I have no recollection of them ever running out of water. (I was the lead for the Cirque aid station for 3 years) I do have many cases where delirious runners passed the volunteers handing out water and then asked the ones 10' further down the trail who only have gatorade if they could have some water. Confusion ensued when the volunteer told them that they only had gatorade, not water. It was not that there was no water, it was that they walked right past it.
So here are the two best tips for hydration in the PPA/PPM:
1) Always be prepared to skip the next aid station. Carry a hand bottle, belt, whatever. Use it between the aid stations and then refill it along the way.
2) As you approach an aid station, start to call out what you want and then listen for a reply. If you want water, yell out for water and a volunteer will bring it to you. Don't be passive.