Let me take a shot at these questions:
1) I don't think there is anything official about this apparent BRT line between SLC and the airport. I think it is an effort to make the 5600 W BRT line look more relevant. The 5600W BRT line, you may recall, is something that UDOT will have to (help) pay for as part of a mitigation from constructing the Mountain View Corridor. Anyone with a map can see that this road is not in an urban environment and does not connect urban environments, and without the mountain view corridor would probably be the last place to construct a higher capacity transit line. But politics being what they are, UDOT will pay for (some of) the construction, and UTA will spend its limited operating budget running it. It is all very silly, and I hope that it isn't actually built for many years (though having it planned now for ROW preservation purposes actually a really good idea).
Anyway, if there is a route from nowhere to nowhere, it makes sens for planners to want to connect it into a larger system, so that it only goes from somewhere to somewhere
through nowhere. So why not connect the 5600 W route via the airport to downtown and the planned South Davis BRT line?
2) This is a proposed extension of the S-Line. If the world had unlimited resources and all proposed transit projects stood an independent chance of being built on their own individual merits, I would be totally in favor of this extension. However, since this project would likely take millions of construction and operating dollars away from other bigger-impact projects (such as BRT down State Street or to South Davis County), I'm not in favor of extending the S-Line all the way to Westminster. There's been some debates about various proposed extensions on this thread, such as
this page.
3) Bus Plus is a great idea that needs to be implemented ASAP. It is basically a BRT line without the dedicated lanes. Buses would use stations on the sides of the road, like a normal bus, but would have ticket machines, raised platforms for level boarding (or at least a smaller step) a better canopy, a message board with accurate arrival information, etc. And the buses would come more frequently, at least every 15 minutes. In more advanced versions, buses would have signal priority at traffic lights so that they wouldn't need to wait at red lights. This type of system makes sense where well-used buses are traveling on low-traffic roads that don't see much traffic congestion. The wonderful thing about Bus Plus would be that stations can come on-line one at a time, meaning that turning a normal bus route into a bus-plus route is something that can be done incrementally. And since it is usually the city that pays for bus stop amenities, individual cities can make bus routes through their jurisdictions bus-plus routes without needing to get other jurisdictions involved at the same time. This is something I wish UTA would be pushing for more, as it is something that the individual cities that want better UTA service can already do on their own, without having to wait for big improvement projects.
Like, the city would say "Hey, UTA, we want better service!" and UTA could be like "Totally. We'll increase service along this bus route from 30 minutes to 10 minutes if you pay for the bus stops to be turned into bus-plus stations" and the city would be like "Okay, we'll improve two stations a year until we get it all done!" and UTA would be like "Deal, baby!" and all the taxpayers would be like "Dude, the bus is cool now. It's like
clean and
safe and
frequent and
easy to understand. I've got to get me some bus plus commute!"
Etc.
Does that answer your questions?
BTW, you have good eyes to spot that stuff on that map.