Hi Simon;
I guess it should work just fine with two abap systems also. Only requirement is web dispatcher configurations to route the requests to the specified remote system.
Using the below link, we can find the details of all the tiles in a catalog.
/sap/opu/odata/UI2/PAGE_BUILDER_CUST/Catalogs%20('X-SAP-UI2-CATALOGPAGE: <catalogid>')/Chips
when accessing it from remote system, we need to pass system alias with the url as shown below
/sap/opu/odata/UI2/PAGE_BUILDER_CUST/Catalogs%20('X-SAP-UI2-CATALOGPAGE: <catalogid>');o=<systemAlias>/Chips
Thanks
Sarbjeet