Here I go with more detail than anyone wants, but you asked! The late-60's loss of the Edgewater/Wisconsin Ave. right of way to the lake is both regrettable and irreversible, so we need to regard street closings seriously and take our time with this one.
A small addition to the pluses: a safer bike path, due to fewer car-bike intersections, but not safer by a huge amount because these are very low-traffic crossings.
The city's saving on maintenance is not negligible because these crossings tend to be very soft -- it's all landfill -- and the places the rails cross the street pavement need endless patching.
The nighttime whistles might be a relatively minor issue because so few residences are close to the crossings. For instance, there are a few apartments on Blount, but the rest is MG&E. We need to listen to residents' comments in this regard.
Another important consideration is emergency vehicle access. If the fire department or police department has big issues with closing the streets, we also need to listen carefully.
The result of closing these streets could be pretty much like where Few Street would cross -- and Few Street just ends. I don't know of any problems this causes. In fact, it benefits the Central Park by making two whole blocks contiguous.
This one is pretty much a "so what" issue unless you live or work right along one of these side streets. If those people strongly dislike the proposal and work against it, their opinion should count for a lot. If they don't bother, or actually like the proposal (it'll make for quiet peaceful cul-de-sac street stubs or totally closed rights-of-way, which might turn out to be desirable) it should be allowed to pass.
I wouldn't be surprised if the negotiated outcome is to close two streets -- Blount and one other -- and leave the third open. Closing Blount would allow the MG&E property on both sides to be contiguous like the area around Few Street, and that always creates opportunity. Leaving one street open could be important for its businesses, or for public safety.
All in all, pretty much a neighborhood issue unless you let long-term annoyance with Wisconsin and Southern color the discussion. (I'm sighing and rolling my eyes here.) It is good the neighborhood alder is trying to slow things down until sufficient comment is collected.