If you are after a higher level of control over the default setting in OWA, EWS offers you the ability to configure many of the default setting by modifying the FAI (folder associated Item) configuration item that controls that setting. One example of a setting that you can modify is the default view of the calendar in OWA eg the following setting
When are user makes a change to this setting in OWA, the setting is stored in an FAI item with an Item Class of OWA.ViewStateConfiguration in a roaming dictionary property called CalendarViewTypeDesktop.
The values for each of the setting are
1 = Day
2 = Week
3 = Work week
4 = Month
The following script first checks to see if the OWA.ViewStateConfiguration config item exists (on a new mailbox if the user has never logged into OWA it probably wont exist).
To use this script you run it with the name of the Mailbox you want to run it against and the value for the enum you want to use eg to set the default as Work week use
./SetOWACalendarView.ps1 firstname.lastname@example.org 3
I've put a download of this script here
The code itself looks like