The Short Answer

For the time being, no, there is no automated method specific to runit.

The Long Answer

There have been several approaches to resolving this.

Using Pre-Built Scripts

The first is to have a pre-built set of scripts. These can be extracted from other projects. Void Linux uses runit as its base init and supervisor, so it might be of interest. There is a project on Github called runit-scripts that might have some of what you need. And I will make a shameless plug for my own project, supervision-scripts, which has a few of them pre-baked and ready, although the project is still being developed.

Using A Framework

The second is to provide a framework that eases the transition of writing scripts. Ignite is a possibility. Also, Toki Clover's Supervision Script Framework (not to be confused with my own project) may provide what you seek as well. In this case, there are no pre-built definitions, but you get bits and pieces of shell script (and possibly other programs) to help you make this transition easier.

Borrowing Existing Scripts and Tools

The third is to borrow scripts from other projects. This means going out and really hunting for them. There are a few out there, but you have to really look.

Doing it the hard way

And finally, you sometimes just have to write it yourself. Frankly, if you're desperate, make a copy of the original /etc/init.d/(whatever) file, set it aside, and edit the file. Typically, at the bottom of a init.d script, you'll find a CASE statement & friends, and from there you can see if there are any weird baked-in command line switches that shouldn't be there but are. Don't bother with anything beyond what is inside start) and stop) in this because they don't apply when using a supervisor. Look around and see if it needs a /var/run/(whatever) directory set up, that's always important too (don't forget to set ownership if you create it!). And towards the top, if the author did it right, there's usually a set of environment variables that contain the real daemon name, along with its options. From there you can usually cobble together a small script quickly.

This has to do with retrocompatibility and, with the scenario where migrating from upstart to systemd could impose a catastrophic failure at Ubuntu 15.04. Quoting the announcement of systemd comming to Ubuntu:

Contingency plan: If after some weeks we find that there are too many or too big regressions, we can revert to upstart by default with two simple uploads (ubuntu-standard and init).

The other detail here is that, Ubuntu did not "fully migrated" to systemd prior to 16.10, having the graphical login to still be managed by upstart not systemd(even with this, being the init manager of choice). Announcement here:

As discussed at UDS 1 we are moving away from using upstart to start graphical desktop sessions, towards systemd (and D-Bus activations in some cases where it's appropriate). Two weeks ago Sebastien Bacher, Iain Lane, Ted Gould, and me had three-day sprint where we converted most services of the Ubuntu session, and before/after I was working on the necessary infrastructure in systemd and upstart, and converted/checked most other flavors. This is now ready to land and get wider testing.

Ubuntu was/is migrating to systemd on a very safe way, first migrating ConsoleKit related stuff back in 2013 to systemd-logind, then migrating the init itself, and the remaining units, to avoid problems.

tl,dr: In your specific case, upstart could be still the one managing graphical login related stuff(lightdm)...