OK, I'm back with some info, having chatted with the account manager.
The short story is that I've had my very strong impression confirmed: Google's house ads are run on the exact same system and under the exact same rules as any other AdWords advertiser. There are no special levers levered, no special buttons pushed, and no special strings pulled.
Just a bit of background for those wondering why this ad seems glued to the top spot: As everyone almost certainly knows, ad rank is not just a function of Max CPC. One's quality score is also very important, and a high Quality Score will usually result in a higher position for an ad. I can't personally imagine any better circumstances for an ad to have an exceptionally
high Quality Score and CTR than these:
A well known and very powerful web analytics tool called Urchin provided by Google, which is advertised by Google, using the name Google in the ad's headline, and urchin.com in the Display URL - and with the ads appearing on Google.com.
As a final note, the ad manager also confirmed for me that we are bidding in line with the high bids for the term at the time the bid was placed, and not
Hope this sets a few minds at ease.