Thanks for your advice. I have the latest NetBSD current packages and sources installed and I'm very determined to get it working..... but without a functional network ...
...it's no fun.
The driver for Linux, broadcom-sta is not very reliable. I experience a lot of annoying connection issues if the network is up. Sometimes everything works well for hours and then my card fails to connect every few minutes even though I believe I've done everything right regarding the kernel setttings and the firmware.
So I guess it won't be a too difficult decision to buy another card which will work. I decided to buy one from Intel.