I assume you are referring to The replacement of the Bosch calipers on Workhorse Chassis. They started replacing them in september of 2010. If you have not received notice it is due to not being the owner of record with Workhorse.
All the information on the recall can be found at
www.workhores.com
There is also a list of select service centers.
Had ours done in October 2010 14,000 miles ago and no issues.
Ther is a great deal of discussion in the Workhorse owners forum.