Different continent here, but I was under the impression that no IFR procedure shall begein below 400 AAL too. IIRC, on the 737, the NAV mode was only available by 400' (U8.5).
Somewhat more recently, while doing business and quality assesment of FMS coding between the 3 large providers, neither do I recall seeing a NAV WPT below 400. And some procedures were quite interesting.