Configuring preferences and options in Outlook.com
FWIW after checking and/or changing every conceivable setting in every account on every device I gave up and kept using the shared calendar as is. Then out of the blue notifications started coming in with the correct (in my case EST) time zone. This lasted for a day or two then reverted back to UTC. Then the occasional notification would come in with EST while the majority were UTC. Now it's back to all UTC.