T-Mobile begins spreading Android 4.0 ICS software update to GALAXY Tab 10.1 (SGH-t859) customers. A day that many Samsung GALAXY Tab 10.1 owners connected to T-Mobile have been waiting for, for a while now. The update changes your tablet firmware build version to T859UVLH6.
The update is available through Samsung Kies software, all you have to is make sure your Kies tool is updated to the latest version before plugin it in, once that is checked plug it in and check for new updates.
More details on how to upgrade to Ice Cream Sandwich check Samsung GALAXY Tab 10.1 support page