It varies widely by device and browser.
I can tell you that that specific example will work in Pocket IE, but that's about the limit of its complexity - it doesn't support DOM handlers, only inline handlers.
Mobile Opera 8 however is almost on a par with its desktop cousin, however you still have a limited range of events, because the devices just can't generate many of them - you'll get click events, focus events if a device has a d-pad, and the usual programattic events like the submit event of forms and the onreadystatechange of an xmlhttp request.
Minimo sucks and blows - I wouldn't waste time with it.
But really - the bottom line here has to be one of practicality - if you're developing for a mobile platform, you need a test device; there's no way you'll be able to do a good job just by asking people to check it every now and then.
So - do you have such a device? What is it running? Is that your target audience?
"Why bother with accessibility? ... Because deep down you know that the web is attractive to people who aren't exactly like you." - Joe Clark