"anyone" can not listen to your cell calls. Only people that have access to inject commands into the SS7 network that your call is routed through can do that.
The expertise to do these things is the domain of well outfitted organizations, who have other simpler methods of making you talk. Indeed, electronic surveillance of is often used to protect agents from dangerous work.
>The expertise to find these kinds of exploits is hard to develop individually.
Yes, but numerous people participating in the Osmocom projects have that expertise. Fortunately, they're interested in building an open-source baseband processor (among other cool things), and not in hacking into anyone's private communications.
It is well know that GNURadio is used by the US navy. I could easily see Osmocom, being used for good or bad - the most important thing being human resources. Although in the case of Osmocom, I'm still not sure how it is related to this kind of hacking.
Did you even look at the OsmocomBB project? It's pretty well-known that the their software (with some alterations) can be used as a poor man's BTS, and so can passively sniff other phones. They're pretty cagey about it, and understandably so since they're pretty conscientious about complying with laws and regs and yet they apparently draw a lot of script kiddies looking to "hack peoples phones signals".
Besides, base stations are available openly on the market now at pretty reasonable prices. It's why I never talk about anything truly private on a mobile phone.
