Works. You can share everything except map cards. One item of note. The 798 unit and TD do not use/have 800mhz. So when the 898 is using the 798s TD via the ethernet settings you only get 83/200/455. When the 798 is using the 898s TD again you only get 83/200/455 since the 798 unit isn't capable of the 800 freq.
What I have in my boat. 898 console/stern TD mount and a 798 bow/TM TD mount.