They cite customer demand as one of the reasons for the push:
“We have seen more customers utilizing and requesting open source notebook solutions in education, government and the enterprise since our ThinkPad T60p Linux announcement, and today's announcement expands upon our efforts by offering customers more Linux options,” said Sam Dusi, vice president, product marketing, Notebook Business Unit, Lenovo
The ThinkPad T Series laptops will be powered by SUSE Linux Enterprise Desktop 10, and are being demonstrated at the LinuxWorld Conference & Expo this week. The new units will be aimed somewhat at businesses but also at the individual user, and are expected to be available before the end of this year. Specific pricing on the units isn't mentioned, nor how that pricing will compare to the same ThinkPad models with Windows installed. You can read the full press release at Novell's site.