Two of the drivers involved in that article are regulars over at The Car Lounge. You can read some of their comments in this post here:

http://forums.thecarlounge.net/zerothread?id=2135351

That post also shows the ratings converted to Standard (USA) gallons as well. Here's the top two:

Corolla: 42.8mpg
Civic: 48.0mpg

What's interesting is that initially we (us posters on the car lounge) thought it HAD to be the Civic HX, but from the pictures of the wheels, and the fact they say it's the same engine as the DX/LX/SE, that would indicate it wasn't even the lean-burn engine! I'd be interested to see what they could have managed with an HX!