You can share using shared tables (SaveDataPerCompany=No), cross-company queries, copying data between companies with DIXF and so on.
Your statement about partitions is wrong; they’re not used for sharing data. On the contrary, they’re used to completely isolate companies. A company in one partition don’t see anything in other partitions (except of a few system tables that are shared even across partitions).
I am guessing they are going to dovetail in MDM for the heavier elements like Customers and Vendors giving greater finctionality than the current limited supporting sharing templates, but as most things AX7 we will wait and see the direction taken.