The move was made to make room on the roster for the recently-acquired Aaron Laffey. Laffey is returning to the team after pitching for them last season.
Laffey will provide the Blue Jays with rotation-depth, which is important as they have an older staff that is likely to deal with many injuries throughout the course of the grueling season.
Laffey pitched for the Mets earlier this season, but was ineffective so they got rid of him. Ironically, Laffey was let go as Shaun Marcum came back from injury to pitch in the Mets rotation, although I am sure that the Blue Jays are very happy to have Brett Lawrie.
It is unclear whether there will be a suitor for Ortiz's services.