How does the BTL-A4 title work with TLt? Can you still attack ships outside your arc with TLT.

No. That title stops stuff like the tlt and any other turret working outside the arc.

Basically it turns your turret into a fixed cannon.

And, importantly, when something says you can do something (TLT says you can target a ship outside your firing arc) and something else says you can't (BTL-A4 says you can't perform attacks outside your firing arc) then Can't always wins.