How to hook into new `CmdlineEnter` Vim event?

With the release of [patch 1206](https://github.com/vim/vim/releases/tag/v8.0.1206) we now have an `autocmd` for entering the command line, which until now the suggestion for an auto-typed `<F12>` has been used to simulate. Is it possible to invoke Cmd2 using these new events, and if so, what steps are necessary to do it?