I too was curious about it and picked one up off ebay in 09. Tried and gave up.
There are fit and wiring issues
Fit:
The bezels have the exact same outer dimensions and mounting tabs, you can plug it right into a vibe, providing you don't have the radio there. The radio opening is different, its wider and just slightly not as tall inside. To make it fit around the 03 radio, I had to remove a little of the plastic stiffeners on the inside bottom of the trix bezel. Even so,it leaves a noticeable gap on the right side of the radio. I assume it would be easier to deal with if you have an aftermarket radio.
Also, the mounting for the three button 05+ trix AC/recirc/rear defrost is different from the mounting for the Vibe AC/recirc, the trix switch doesn't fit into the vibe bezel
Wiring:
The connectors for the rear defrost, hazard lights, and AC/Recirc mate up just fine between the two bezels. The rear defrost and hazard lights work on the trix bezel, but not AC or recirc.
The AC button latches, as it does on the vibe, but the green light doesn't light up, and it does not engage the compressor clutch, so there is some electrical difference between the two switches
The recirc button on the vibe latches in or out, the trix one is a momentary switch, if it did work, it would only do so as long as you held the button in. However, even if you hold the button in, the fresh/recirc actuator does nothing, so there'd really be no point in holding the switch in.
I never bothered trying to figure out what the differences were and what sort of interface would be required to get the trix switch to work with Vibe AC and recirc. It may be just wiring, it may be adding some actual circuitry
The trix one doesn't support the mechanical cable to disable recirc when in defrost mode, which doesn't bother me since I almost never use recirc, and I always have that mechanical cable disconnected from the bezel anyway.
Don't know if the 03-04 trixes used the same failure prone fresh/recirc actuator the 03-08 Vibes did, if so, perhaps Toyota switched to something more reliable for the 05+ trixes. Perhaps a stronger motive for the change in the trix bezels was so Toyota could make the radio optional while still providing a clock.
As MacGyver pointed out, there is no connector for the passenger airbag light, and no wiring for the clock. According to the wiring diagrams, the passenger airbag light is just a light that lights up when the front passenger seat weight switch senses something heavy enough to possibly be a person. DISCLAIMER: I have never had an airbag deploy, ever, so if you disconnect the light and it somehow disables the passenger airbag, its not my fault. Looks like the trix bezel uses the same connector for the clock and the passenger airbag light
If you're adventurous, I'll sell you mine for a small fee plus shipping, the one I have has been sitting in my garage gathering dust for 8 years until today. But honestly, while we both had the same idea, my advice is to not bother.