Oh, it wasn't just the satnav.
When GM developed the Epsilon platform for small/midsized cars, they knew Saab was onboard to use it for the 2nd-gen 9-3. Saab also always had a 900/9-3 convertible, so it was assumed that other GM divisions could borrow from Saab's work for their own sporty/convertible Epsilon-platform models.
Nope.
When the GM North America guys saw the BOM for the 9-3, there were enough changes from the shared Epsilon components list that there was no economy to be gained by sharing the parts with the Pontiac G6 convertible. Saab made lots of expensive changes to the structure, supposedly.
But...people seem real happy with their 9-3 convertibles; happier than the few I've met who've experienced the G6.
I think Bob Lutz, in one of his books, talks about how Saab insisted on doing lots of things themselves or going with a different vendor than GM NA or GM EU. Like the previously-mentioned satnav, HVAC components, power window regulators..
things where some other part of GM would have a cheaper part that was better tested and likely more reliable, and that the customer would never see. Of course, GM should have let Saab continue doing its own interior trim, including its fantastic seats. And they did make Saab their center of engine control electronics and turbo powertrain development, for a time.