I'm not talking about local law enforcement here though I believe it will get this easy for them someday.
Given the NSA and its easy access to all computer databases, let me speculate at all the ways a hobby phone can be traced to you in a matter of one hour of usage or less, probably seconds but I don't know. Then, all the calls made by the hobby phone are likely yours -Nailed
1. You have a hobby phone in a late model car with GPS. Ping three towers and triangulate on hobby phone, correlate that with car GPS position and ownership. Nailed!
2. You carry a hobby phone in your non GPS car with your personal phone, leaving them both on. (Can they be traced if off?) Match that position after 3 tower changes - Nailed
3. You use your hobby phone surreptitiously at home, work and restaurant you used your credit card. Nailed
4. Use of hobby phone time and date at restaurant along with personal or work credit card usage. Nailed
5. You use a new hobby phone but call the same numbers you called off the old phone from the above locations - nailed
I could go on and on but the moral of the story is - you are being watched, boys - don''t piss off the wrong government agency.