Other Symbian Foundation members include Texas Instruments, Vodafone, Samsung, LG, and AT&T (yep, the same AT&T that currently sells precisely one Symbian-based phone), so things could get interesting. The move clearly seems to be a preemptive strike against Google's Open Handset Alliance, LiMo, and other collaborative efforts forming around the globe with the goal of standardizing smartphone operating systems; the writing was on the wall, and Symbian didn't want to miss the train. Total cash outlay for the move will run Nokia roughly €264 million -- about $410 million in yankee currency.
Update: It's worth noting that the foundation plans to make the entire platform available as open source in the next two years -- "select components" at launch.
Read - Creation of Symbian Foundation
Read - Acquisition of Symbian by Nokia