I went to http://techinfo.toyota.com and I've downloaded the repair manual and wiring diagrams for '05 Prius and what I've found out is that the Prius'es radio uses the standard Toyota Audio connectors (year '87 and up). It uses additional connectors for connecting with the display control and with the controls on the wheel, but these connectors are separate.

So it looks like there should be no problem hooking up my Alpine unit to it.

I'm going to install it this weekend and I'll let you guys know how it went.

Regards
Dmitry