See PHI2006. An install reports that Perforce support no longer appears to function:
$ arc land STRATEGY Merging with "squash" strategy, the default strategy. SOURCE Landing the current branch, "test". ONTO REMOTE Landing onto remote "origin", the default remote under Git. USAGE EXCEPTION No pushable remote "origin" exists. Use the "--onto-remote" flag to choose a valid, pushable remote to land changes onto.
This is supposed to work, but testing was, charitably, cursory after the "toolsets" changes to "arc land".