I don't think it means much either way. I think DT just saw an opportunity to open for/latch onto one of the biggest rock acts in the world as a means of exposing their brand to a wider audience. Dream Theater has cited Iron Maiden as an influence from the beginning of their career, so the affinity they feel for Maiden's music is really nothing new.
Besides, the Prognation lineup that DT took out with them last summer was more proggy than not (ZPZ, STS, etc).