Company wide calendar and contacts

The way you would do this would be to create a shared mailbox, then import the calendar items into the mailbox's calendar. You would do this by creating the mailbox (Exchange Admin > Recipients > Shared > Create new mailbox). You should be able to assign full permission to the mailbox when creating it (This would be on the Delegation tab, under full access, I believe). Once the mailbox is created, open it up in Outlook. Open the Code-Two calendar in Outlook, then change the view to "List" view. Once the view shows up, hit CTRL-A to select all items, hit CTRL-C to copy the objects, then open the shared mailbox's calendar in Outlook, select the list view for it, and hit CTRL-V to paste the calendar entries. Once the calendar is populated with events, right click the calendar, go to Properties, then select the Permissions tab and set the permissions you want. If you want everyone to be able to create calendar entries, click Add... then select a group that has all the users in it (You will need to create this group in O365 first), select okay. Highlight the group you added in the list of permissions, select Full Permissions under Read, Create Items under Write, and Own under Delete Items, then click apply to complete the permission set. https://support.office.com/en-ie/article/share-an-outlook-calendar-with-other-people-353ed2c1-3ec5-449d-8c73-6931a0adab88 has some details on what the permission levels do and how to operate the permissions view.

Once the calendar is added to this shared mailbox (You don't need to assign a license to the mailbox, btw. Shared Mailboxes are free), users can add it in Outlook by going to Calendars, right clicking on Other Calendars, then select Add Calendar > From Address book and find the shared mailbox in the address list. Select it and it will show in Outlook.

To do this on phones, you have to have Outlook for Android or iPhone and is done by going to the calendar view, Clicking on the three horizontal line icon in the upper left, then clicking the calendar icon with a + sign on it. Select Add a shared Calendar, search for the shared mailbox, then click the + button, and it will show in the calendar view. Users can set the color the want to use for showing appointments in that calendar.

Let me know if you have any questions.

There is no perfect solution here, especially when mobiles are involved. PFs work fine in O365, but you will need to use the device browser in order to get access to them on the mobile. If in-app access is a must, then you can use the new Calendar sharing model and improvements made for the Outlook app - store the calendar items in a given (shared) mailbox, then add permissions accordingly and open it via the Outlook mobile app. Sadly, Calendar is the only folder type that supports shared access on the mobile for now, so this wont work for contacts.

Contact addition is a little more difficult, as it involves creating contact objects in Office 365. https://www.experts-exchange.com/questions/28599544/How-can-I-import-all-user-contacts-from-outlook-into-global-address-list-in-exchange-2013.html has a script that can be used for this.