That looks like a posted ridge -- so there wouldn't be any tension in the "tie". If you are clear spanning with a truss, the situation is different.
It takes an extremely serious scarf to join a tie beam for a truss of any size. We built some 36' kingpost trusses recently (with a continuous tie) and under design loads there is 15,200 lbs of tension in the bottom chord. And we don't have any snow loading to speak of here.
One way you could do it is a really long (maybe 4 feet or longer) tabled scarf with shear blocks or split rings. But to deal with 15.2 kips you will need 3 or 4 shear blocks and enough of a shear plane between them to develop enough capacity. It takes through bolts or steel bands to keep the pieces clamped together tightly.
Maybe some of the bridge guys can dig up a photo of a bottom chord scarf (Will - are you out there?).
