Finding Telephone Numbers with WIreShark

Probably not. A Blackberry, like other mobile computers, has multiple network interfaces, and if it's using one network interface (Wi-Fi), that doesn't say anything about its other network interfaces (mobile phone interface) - you can get the Wi-Fi MAC address for the Blackberry from a network capture, but, unless some network traffic from the Blackberry happens to announce its phone number (and I'm not sure what traffic that would be - the user could, for example, be e-mailing their phone number to somebody, but they could be e-mailing a home or office landline number, or somebody else's phone number, or...).