Not a full answer but from PGPSW:-
"As far as the TomTom units are concerned, it contains information that the HOME application uses.
If a .tlv file is removed it doesn't stop that function from working"

and also from there:-
"From personal experience in the UK, the .tlv files are only used by Home as a sort of "index file". They let Home know where they were downloaded to andfrom and also contain the secription that Home shows you if you click on "More info..."

But I've seen reports from our transatlantic cousins, where they say that sometimes the .tlv file IS needed for US/Canada maps to work if you have copied them to your PC and then back again"