Microsoft Online Services team published a white paper about Public Folder migration to BPOS. By the way, Public Folders are not supported which means that this documentation will explain how to work around and use Sharepoint Online Services.
About The Author
Anderson Patricio is a Canadian MVP in Cloud and Datacenter Management, and Office Server and Services, besides of the Microsoft Award he also holds a Solutions Master (MCSM) in Exchange, CISSP and several other certifications. Anderson contributes to the Microsoft Community with articles, tutorials, blog posts, twitter, forums and book reviews. He is a regular contributor here at Techgenix.com, MSExchange.org, ITPROCentral.com and Anderson Patricio.org (Portuguese).