I don't have or use illustrator, but I know Corel Draw has an option if you export a cdr file as an ai file a box comes up asking what ai version to save it to. It goes all the way back to illustrator 88 (I think that's it) then other programs can read it.
Whenever I have asked for a file to be saved in an older, more compatible version of illustrator, I always get the same look / stare/ or silence on the phone, like they have never heard of that before.
That and asking them to "convert to curves / outlines" gets you the same blank stare.
I assume that illy gives you the option to save in an older version.