I was looking at the illustrations for Sugarhouse Streetcar, and the criticism that UTA only knows how to build light rail sings true. Sugarhouse Streetcar looks like a TRAX line--a dedicated corridor, with a gravel bed and fences along both sides. I've ridden streetcar systems in Portland and Barcelona. Like the name suggests, streetcars run in the street...sometimes on the edge, sometimes down a center median.
UTA built most of the TRAX system using old railway corridor (Sandy--SLC--Mid-Jordan) and seems to be comfortable and familiar doing so. It certainly makes sense to do so. Building in an existing corridor reduces utility conflicts, and makes the property acquisition for right of way relatively simple.
Cost-wise, I know that the per-mile costs associated with running TRAX light rail through Salt Lake City on city streets was fairly high compared to the initial Sandy-Salt Lake stretch, and certainly more complex in terms of traffic engineering, and the need to come to negotiated agreements with UDOT and Salt Lake City.
The next phase of the Sugarhouse Streetcar will have to be along roadway (east on 21st, or north on 1100 East), so UTA is going to have learn how to build 'real' streetcar, and not just TRAX-lite.
TRAX shares right of way with automobiles only at intersections
(typically left turn arrows). The rest of the street right of way is
protected by curbs or jersey barriers separating the train from
auto-traffic. That wasn't originally so, but a two or three
cars got themselves t-boned as they tried to make (illegal) turns across
the TRAX right of way). Hence, curbs.
But that's not something that is going to work with streetcar, which is going to have to run 'in traffic', right with the cars. That it is possible to do so is really the big difference between the two vehicles.