I never noticed the car pool lane thing as it relates to the plug in Prius. However I did covertly watch a PiP driver leave a little note under my wiper blade, at work.
(btw our paid "charging at work" rules state there is no requirement to move a car that is no longer actively charging. The rationale is it may take away from work - as some people would have to travel quite a bit of distance to undergo the "unplug and remove car" objective ... and so our workplace Chargepoint EVSE's only bill us for actual kWh's drawn - rather than actual hookup time)
In short - the pre written / printed note told me I should not be there unless I'm actively charging. By choice I start at 5 a.m. - specifically so I always have an empty charge spot available. After all - no one in their right mind would willingly wake up at 3:30 a.m. unless they wanted to assure their parking stall
by noon - all workplace charged spots are full.
I have to admit - it kind of made me smirk, thinking someone with an alternate fuel source - who can easily get home w/out electricity is bugged with me always being in "their" way.