Yes, there are manufacturer and carrier contractual obligations that prevent this from happening as of now (October 2012), but...
In theory, one should be able to get an iPhone working on Ting with a donor phone (from ting), and an unlocked/jailbroken iphone 4S (from ANY carrier).
Shouldn't we be able to
- buy suitable donor phone from Ting
- BYO-iPhone from *any* network
- reprogram with donor ESN/MEID/IMEI and data profiles (using something like CDMA tool)
Maybe it involves jailbreaking, maybe it involves hacking yet deeper parts of the firmware. I don't know. Multiple threads have information leading to successes of this with other phones. Isn't someone far off with an iPhone?
Ting will not be able to encourage this process outright. Let's figure it out, eh?