Do the math
A program like this isn't designed and implemented in two weeks. If you ask around, the existing partners heard about this at their April partner event (cf. http://blog.openitstrategies.com/2008/07/symbian-new-ecosystem.html) That mean the program was being developed since January or even earlier.
Also, plans for the Nokia acquisition didn't leak -- implying that the knowledge was held by a small number of people for a relatively short period of time (weeks, not months). So the rank and file working on the new ecosystem might not have heard about the acquisition until the new program was already done.
You might ask a Symbian spokesman: I'm sure they'd tell you.