Without thinking about it too much, I'd probably say that the way you'd want to code the functionality is like this:

module triState (a,b,sel,out);
input a,b,sel;
output out;

wire out = sel ? a : b;

endmodule

that will give you a mux though not a tristate buffer. I think that what it comes down to is that if you have the hardware resources then the synthesizer would know how to utilize the tri keyword. In all cases if you're set on a tristate buffer you would need to make the wire of type tri. Check out this link:

http://www.altera.com/support/e...state.html

D