It’s become clear from comments that there’s some confusion about what the streetcar and BRT modes in the TMP actually mean. It is not, in general, the service quality of the South Lake Union Streetcar. You have to dig into the pamphlets to which each post links to understand what treatments the streetcar (or BRT bus) would receive.
In the case of the 4th/5th couplet, there are two options. The best one, presented at right, has a dedicated transit lane in both directions. The other alternative would do so only on 5th.
For cost reasons, in that project we’re likely stuck with the current configuration through SLU, unless one of the other lines is built.
As for Ballard/Fremont, the plan envisions dedicated transit lanes in the Ballard/Leary couplet, on Westlake between Valley and Nickerson, and on one or both avenues downtown as above. Elsewhere, it would operate in mixed traffic, although it would get other priority treatments like queue jumps and signal priority.