Warning (15610): No output dependent on input pin

The reason is simple and can be seen in the below always block. There are multiple assignments to each x_bus_out, but only the last takes place.

always @ (TAU_A, TAU_B, TAU_C, TSR_A, TSR_B, TSR_C, TR_A, TR_B, TR_C, tau_w2, tsr_w2, tr_w2)
begin
	if(TAU_A == 1)
	begin
		A_bus_out = tau_w2;
	end
	else
	begin
		A_bus_out = 12'hzzz;
	end
	if(TAU_B == 1)
	B_bus_out = tau_w2;
	else
	B_bus_out = 12'hzzz;
	
	if(TAU_C == 1)
	C_bus_out = tau_w2;
	else
	C_bus_out = 12'hzzz;
	
	/////////////////////////
	
	if(TSR_A == 1)
	A_bus_out = tsr_w2;
	else
	A_bus_out = 12'hzzz;
	
	if(TSR_B == 1)
	B_bus_out = tsr_w2;
	else
	B_bus_out = 12'hzzz;
	
	if(TSR_C == 1)
	C_bus_out = tsr_w2;
	else
	C_bus_out = 12'hzzz;
	
	//////////////////////////
	
	if(TR_A)
	A_bus_out = tr_w2;
	else
	A_bus_out = 12'hzzz;
	
	if(TR_B)
	B_bus_out = tr_w2;
	else
	B_bus_out = 12'hzzz;
	
	if(TR_C)
	C_bus_out = tr_w2;
	else
	C_bus_out = 12'hzzz;
end	

  if(TAU_A == 1)
    A_bus_out = tau_w2;
  else if(TSR_A == 1)
    A_bus_out = tsr_w2;
  else if(TR_A)
    A_bus_out = tr_w2;
  else
    A_bus_out = 12'hzzz;