I've been following the VIA 50/50 seating arrangement debate on another forum. I'd hate to be travelling backwards for 4-5 hours, and you're still unable to choose your own seat unless you book online, then call customer service if you don't like your seat assignment. (I often do this when I find that the seat automatically assigned to me ends up being one where the window doesn't line up.)
The reason why VIA wants to implement 50-50 seats is so it can quickly reverse trains without wyeing them; Montreal Central Station being the best example. Trains will usually pull into the station, unload, reverse to Pointe-St-Charles, wye, and back into Central for the next departure. I've been on trains from Toronto that wyed at Pointe-St-Charles before unloading us at Central Station. VIA has to wye trains on the corridor at Quebec City, Ottawa, Kingston, Toronto, London, Sarnia, and Windsor as well.
(Sidenote: VIA's Canadian is not wyed at Toronto, despite it being the terminus of that train. That's why it heads straight down the Bala Sub tp Union, unloads, continues to the TMC at Mimico for cleaning, servicing and maintenance, and backs in to Union for the next departure, running up the Newmarket Sub, changing to the York Sub at Snider - it backs up to make this connection - then up the Bala heading north-west.)
But how does VIA then want to reverse trains without wyeing them? They'd need new bi-directional locomotives, locomotives on both ends in "top and tail" operation, or cab or "cabbage" cars. Or they'd have to detach the locomotive, wye that, and run it around the passenger cars. Instituting 50/50 seats before figuring this out seems bass-ackwards, and isn't customer-friendly.