That's right you heard it here first we finally have ICS with working data on the HTC Thunderbolt 4G! Although it's not quite 4G LTE the reported "1x" is getting speeds over 1mb/s which is enough for most casual activities. Most likely 3G is getting reported as 1x based on speed tests by multiple users. While we are waiting on an Official Ice Cream Sandwich update with Sense 3.6 from HTC we have a new build of ICS built from source from the hard working members of the development community Liquid0624 and SP-Jester. It's been a long time to see this released and we all look forward to new bug fixes and feature updates on this rom. The links to the download and forum post are below.
XDA Forum Post and Download
Update: One of the users discovered if you switch it to EvDo only it will display 3G some people are reporting speeds as fast as 2.7mb/s download and over 3.5mb/s upload. We should have 4G LTE very soon with this new break through.
Update 2: It's been pretty well confirmed you can get 4G speeds on this although it will never say 4G or 3G it will always say 1x. It is in the process of getting fix and we should have a new build from source soon.