Dear jaranet
"observational studies fall squarely under the evidence-based umbrella. With large samples and adjustment for differences between comparison groups/changes over time, they can provide very robust results."
I guess your terminology threw me. I consider information obtained from observational studies akin to "anecdotal evidence". But if the studies conform to normal survey and sampling rigour I yield. And I hope the "WADoH (in partnership health researchers" study gives defensible results down the track.

"Evidence based" essentially means drawing on other's experience.

The problem with randomised trials is that they take so long and are subject to so many assumptions that may not apply to everyone, that any attempt to base policy on this will simply result in nothing happening.