If both devices are working correctly, and within spec, then they should not interfere with one another and you'd expect them to coexist in the same room or work area. You have already identified that a Blackberry device operates on a different frequency band to a WiFi 802.11b/g device. The very occasional problem with 2.4GHz cordless phones occurs because they're using the same band as b/g WiFi, albeit different channels. In other words, the devices are very much closer together frequency-wise.
However, it is remotely possible for a poorly manufactured, badly setup or damaged Blackerry transmitter to throw out spurious and unwanted signals on frequencies and bands other than those for which it was intended. Ditto WiFi equipment. This might cause signal blanking or interference to another device. Don't have figures available re power output, but I'd say the Blackberry will be transmitting with a higher RF output in terms of milliwatts, than a WiFi device.
Unlikely problem, but possible...
ROGER - G0AOZ.