Bloomberg cites two sources with knowledge of the matter as saying Williamson will take on a managerial position within Facebook's mobile-software group after being hired in the "past couple of weeks."
Williamson was fired from Apple in November following the iOS Maps rollout, which was widely panned due to incorrect location data, poor routing assets and Flyover rendering issues.
Facebook is looking to strengthen its mobile offerings, as evidenced by the latest "Facebook Home" initiative on Android. Certain features from Home were added to the flagship Facebook iOS app on Tuesday, including so-called "Chat Heads," which allow for easy access to ongoing Facebook Messenger conversations.
As noted by the publication, Williamson isn't the first former Apple employee to be hired by Facebook. Currently, iPhone touch-screen UI developer Greg Novick, iPhone software gurus Tim Omernick and Chris Tremblay, and creator of Apple's first-party Stocks app Scott Goodson have joined the Facebook team.
In addition, Push Pop Press founders and former Apple designers Mike Matas and Kimon Tsinteris were added to the company's roster after their firm was acquired by the social network. Finally, Facebook's head of consumer marketing, Rebecca Van Dyck, was also an Apple employee.