According to this (press release style) article, "Canvas LMS is now the only learning management system that has the Google Assignments integration." Basically it is a Google Drive integration with the LMS. I don't know why LMS publicity departments love this sort of 'exclusive' functionality - it just promotes a silo mentality when we should be pursuing interoperability. At any rate, since this is just being done using LTI, unless Instructure paid Google some extra money, this sort of functionality will be available in other LMSs as well. More here.