Why is it unlikely? Nigel definitely got the Dalcon in 2005 or 2006. The forum thread that discusses the console and Nigel’s purchase from 2006, and there are a bunch of photos showing it in use during the recording of In Rainbows (and in fact, it was the main one used during those sessions).
Thom says that the console used on Bodysnatchers was a “wicked old mixing desk that [Nigel] managed to get off a studio in L.A”(XFM Jan 3, 2008). The Dalcon fits that description very nicely, being a unique and old mixing desk which Nigel got from Ocean Way Hollywood (in L.A.).
You are correct that the Audiotronics was used during the In Rainbows sessions. However, unless evidence is found that Nigel also purchased the Audiotronics from a studio in L.A., I think that we should go with the Dalcon (though it is possible that Thom confused the two).