So you have a Nexus S 4G and you want to bring it to Ting. Here's how I did it through the BYOSD program, without needing a donor phone (ala https://help.ting.com/entries/21256192-nexus-s-on-ting-working ). This is because the Nexus S 4G has been added to the whitelist, possibly in the last two days or so. You'll need:
A Nexus S 4G with a clean ESN
Your phone's decimal MEID (under the battery, or on the bottom of the box)
Your phone's MSL (which you'll get through Ting)
Some patience (about 12 hours worth).
Edit: And you need to meet the other requirements of the BYOD program (inactive Sprint account, etc.)
Here's what I did:
Charge your Nexus S 4G to at least 50 percent. Turn it on and update it to the latest version of Android (currently, 4.1.2). You may need to create a Google account, and connect it to your local Wifi network in order to do so.
Go to http://www.ting.com/byod and select the Samsung Galaxy S II Epic 4G Touch as the phone you're bringing over. Complete the six step wizard, entering the decimal (not hexadecimal) MEID when prompted.
At the end of the wizard you will receive an error in a red box at the top that says "device activation in progress". This is normal. Call or email Ting support and tell them you need the MSL for your phone while you wait. Write that down and close out of Ting for now.
You can check the status of the device in your Dashboard --> Devices section - it should say either "pending" or "not yet activated".
After about 12 hours (I waited overnight), log back into the Dashboard --> Devices section, and click "activate now". Skip to the last step, 6, by clicking the appropriate box at the top. Click the "Activate" or "Confirm" button near the bottom to continue and you should receive the "Congratulations" screen and welcome email from Ting. If you don't, wait another hour or so to try again.
Go to your phone's settings, and under "About phone", tap "Sprint system updates". Tap "Update PRL" (and wait for it to complete) and then "Update Profile" (and again wait for it to complete). Open a browser and wait for the final PRL configuration. Then restart your phone.
At this point, 3G data, SMS and voice should be working. If it isn't repeat step 6.
Go into your phone's settings, click "More..." under Wireless & Networks, tap 4G settings, and tap the 4G check box to ensure the WiMax radio is on. Exit back to home.
Go to the dialer and enter *#*#3282#*#* (*#*#DATA#*#*).
Touch Edit and enter the MSL you got from Ting in step 3 above. Tap "Others" and then tap "MMSC URL". Tap "mmsc", and replace the existing with "http://mms.plspictures.com" (minus the quotes). Click OK when done.
Press back three times to get back to the "Data Programming" menu. This time, press "View".
Tap WiMax and enter your MSL from step 3 above.
Tap Realm, and then press the physical "Menu" button (second from the left, between back and search). Tap "WRITE Rlm" and enter "mvno102.sprintpcs.com" (minus the quotes). Click OK and back out to the home.
Reboot the phone and give it a few minutes to settle down.
At this point of time, you should have working voice, SMS and MMS, 3G data and 4G data. A good way to test that your 4G radio is working is to make a call and open the browser at the same time: if you can load a page while you are on a call, your WiMax radio is working; if not, redo step 9 and 11-13 above.
I hope this helps someone. I know a lot of us who share the desire for a truly revolutionary cellular service, like Ting, are also those who enjoy getting our unadulterated Android direct from Google and I am grateful to Ting for having worked with Google and Sprint for making Nexus on Ting possible.
I'll try to help as much as I can, but please note that I'm also a n00b to Ting.