Hi fob,
MacOsX is very… "shy" with autostarting anything, I think that is for your own safety… mp4 is just "data", meaning, you want your Mac to open a file "from the mean outside world" automatically… no, don't think so…
Different with video-cd/dvd: a designated "video only" disc can start by itself, iDVD and DVSP offers such possibilties. but video-cds/dvds cannot contain mp4, you have to convert your file…
AFAIK, Toast lets you burn "windows" cds, but I have absolutley no clue, how to generate .inf files…