dtproperties is actually built by SQL-DMO, which is used by SQL Enterprise Mangler to do virtually all of its tricks. The net result is that it is effectively a system table, even though it isn't used by the SQL engine itself.
drop table dtproperties runs fine from QA. I started EM on the DB but the table didn't show up.. so I stopped & started the server and voila, a dtproperties table. Funny thing though: went for a second try to confirm: alas, no dtproperties table.