I also think the value for Google here isn't revenues so much as controlling another piece of the internet transactional infrastructure.
This must still be a huge win for the founders. They probably still had most of the equity since they only took one round of financing, and at a point when the company was already mature.
Dan Wienreb did a very interesting talk, "Lisp for High-Performance Transaction Processing" that covered it and a bit on the future of Lisp (for a outline and link to the talk see: http://xach.livejournal.com/225634.html).
RES is a three tier system with Oracle RAC as the backend (pretty much the only choice), stateless Common Lisp middleware and Java with the usual web libraries for the front end. 300 milisecond? general max transaction time, which they weren't finding to be a big issue even with GC.
The problem: someone has to go first. While it's arbitrarily sized/scoped to accommodate American Airlines, Air Canada was going to be the lead customer. In August 2009 they suspended their participation in the project, I strongly suspect due to the general recession/depression in the industry. Switching would be very expensive in all sorts of ways and raw survival almost certainly is taking priority. (ITA has continued developing the system.)
This part/project of ITA is very likely to be a victim of bad timing; I sure can't see Google credibly continuing it, it's all wrong for their service culture, although perhaps it'll get spun off.
EDIT: Mind you, I've only heard of the aversion to lisp, so have no data to back my claim up. That said, it has been mentioned several times on HN: http://news.ycombinator.com/item?id=1282583 http://news.ycombinator.com/item?id=363023
That's completely different to Google buying an existing business for $700 million whose core tech is written in Lisp.
However, it's reasonable for them to be averse to writing totally new projects in Lisp, in-house, because when you're at a huge company as a general rule you don't want dozens of different languages in use: it's inefficient and you lose out on a lot of opportunities to leverage skills across teams and across service layers if you do that. Lisp, from what I heard, didn't make the cut, despite it's strengths. They still allow a few though, and I believe they are Python, JavaScript, Java and C/C++.
... not any more!
But the oracle RAC (just guessing here) may act as a cache between the 300 ms part and the actual tables, and to be a fat reliable pipe.
But they do take on some interesting problems, such as how do you keep this up across system upgrades, hardware failures, application version migration, among others.
That might make migrating from Oracle to BigTable a bit easier.
Btw, many of the PSS vendors already have or are currently in the process of renewing their "expensive mainframes with ugly old code bases".