I have not heard of any place that allows an AEMT to manually defibrillate or interpret a 12 lead. However there are many states that still use EMT-Intermediates, which is no longer a National Registry recognized certification. Many states still certify and train intermediates though, and in some places an Intermediate as almost an identical scope to paramedics but they have to call for most treatments.
As for CT, I have no idea. In some states it's up the region to set protocols for its providers, in others it's a statewide set (like MA).
AEMTs in might part of Colorado don't have a significantly greater scope than our EMTs as EMT with IV endorsement (very common, nearly every paid EMT has it as do many volunteers) can start IVs, initiate and maintain fluid infusions, start IOs (in my area), give IV naloxone and dextrose, Zofran ODT and IV in some areas, and nebulized albuterol (with orders). AEMTs add SL nitro (not the patients), Benadryl, Atrovent, Epi-1:000 ampules, and Zofran IV. All AEMTs can start IOs and EJs as well. That's about it for differences, and they aren't particularly common.
I would however like to see EMT-IV go away and be replaced by AEMT so we could be operating in line with the rest of the country.