The rear O2 sensors don't check for temperature, in fact, they are probably electrically heated for quicker light off. They look for oxygen also and their signal should be a function of the upstream O2 sensor, but with less swing in O2 deviation and delayed in response time. The system checks for O2 variations, so a fixed voltage won't fool the system, and "excuses" excursions due to full throttle enrichment.
A tailpipe test is only performed in closed loop, so the fuel system would (try to) adjust for any leaning you might try with the fuel. Basically you are hoping that changing from "gasoline" to "gasohol" with 2.7% oxygen will make a difference, but the engine is smart enough to adjust for it when warm.
In New York, up until now, many counties used a "visual" inspection for emissions. Stuff had to be there, but there was no test for performance. Otherwise, it would be highly unusual for a non-catalyst engine to meet the tailpipe standards.