I assume that the 4 biggest GA areas in the world are the US, Europe, Canada and Australia - in that order. The comparisons are a bit rubbery because different country's have different aircraft registration definitions (ie Australia does not count RAA registrations, but some other countries do).
Australia seems to be completely on its own in mandating ADS-B for GA and for IFR below 10,000 ft.
WHY?
And given that no other major country seems to be adopting Australia's "one size fits all" regime, I would assume that the rest of the world has found a way to accommodate non compliant aircraft like Dick's Citation.
I agree that ADS-B has benefits, but why the rush to implement a blanket solution in Australia before the mandated equipment is readily available????
Here is the roundup I have found:
The US is implementing ADS-B by 1 Jan 2020 in class A, B & C airspace and in class E only above 10,000 ft.
See here:
ADS-B Frequently Asked Questions (FAQs)
Europe seems to be bundling ADS-B implementation in with the "Single Sky" policy via EASA. Its a bit hazy to me, but I can't see that Europe ever intends to mandate ADS-B for aircraft under 5700 kg / 250 kt cruise speed, although implementation into GA still seems to be in debate.
See here:
http://www.icao.int/APAC/Meetings/2010/adsb/sp22.pdf
Canada
No current plan to implement across domestic airspace.
See:
http://www.midcanadamod.com/sites/de...or_posting.pdf
Some useful summaries from Honeywell
http://pages3.honeywell.com/rs/honey...%209-2013.pptx
And Boeing
http://www.icao.int/APAC/Meetings/20...12%20Final.pdf
And Boeing again
http://www.caac.gov.cn/dev/fbs/xjsyy...0147660674.pdf