Last September three of us on bikes rode through there (I-15) Morning rush hour.
We found the HOV lanes to great (at least we had a wall there and not someone cutting in) but we weren't 100% sure if we should have been in that lane.
Every city seems to have different reg's as to who can ride there.
I know motorcycles can't ride in the HOV lanes in Toronto.

You were OK in that lane. There are signs in the lane saying "Motorcycles OK".
They can only drive solo if they pay for the C plates. Or get the transponder and pay per use.
When they made it a pay-to-use lane that was the end of any benefit it had.

Sure seems that way. Having all these other users in the lane also makes it harder for people to tell who is supposed to be there and who is not. Used to be you could easily see if there was a passenger or not, and now since you can't tell it's a free-for-all and people are happy to take there chances like any other traffic law. Oh well.