I don't know LA enough to comment on that project, but my experience with similar projects is the bike trails created like that are a beautiful ride to nowhere. A great trip to take on a nice Saturday, but nobody will use them to get anywhere. (other than the bars that happen to be near the trail)
That's my experience as well. My town converted an abandoned rail line to a biking/walking trail. It does run through downtown, but beyond that it basically goes noplace very desirable. It gets recreational use by a small subset of the community, but it's not a big difference-maker in making cycling practical.