When Google released the Jelly Bean source code it looked pretty obvious that the Nexus devices would be the first to taste the flavor of a new version of Android, Jelly Bean, but after the update released for Galaxy Nexus and Nexus 7 the users of the older Nexus devices started to wonder when the update will release for their device. But now the official Android Jelly Bean OTA has been released for the Samsung Nexus S.
Apparently the OTA appears to be for the i9020T and i9023, according to report i9023 variants of the phone should be able to upgrade and there’s even a link for the file to Google’s servers. It also appears that i9020T flavors can also use the refresh. Anyway if you are not patient enough to wait for the update to roll out for you then you can check out this thread or either this thread that both has the download links for the OTA.
Source: XDA Developers