The fact that we indeed see Triscene further approves theory about short war between Ethernals (mainly forces under their command) and T'Leth. T'Leth tech was captured, not all of it, but enough to get dinosaurs.
I don't think they Will ever fight. They are both on the one side - The Empire. AFAIK, T'leth presents on Earth much longer, than The Martian base. I suppose, this "city" is Just older and obsolete(by Star God's means) conquest-colonisation tool. And its commander is second-in-command to martian brain. So, it activates and starts "conquest procedure" when his supreme commander becomes non-functional.
About the use of T'leth weapons and tech - almost every modern-day country keeps lots of obsolete weapons in reserve storage bases. In case of big war, obsolete firearms will be issued to secondary and tertiary troops, national guard, recruits, old tanks, guns and trucks will see some use. Also, today you can see and sometimes buy not only WW2-era $100 Mosin-Nagant, buy even flintlock muzzle-loaded firearms. So, why shouldn't aliens use old buy good things?
And that'ts the moment when we can see biodrones and tasoths - If you piss off big factions long enough to become "Major disturbance factor", Star Gods may use some more of their power - wake up some operatives and give the command to seek and destroy this nasty pirates.