General Description: To what does the warning "wired or in net = <signalname>" refer?
This warning occurs when the user attempts to tie two signals together. Even if the two signals are both tri-stated, this warning will occur. Two signals cannot be tied together via tri-state internally because each macrocell has only one tri-state buffer; this can either go directly to an output pad or back to the interconnect.
A workaround would be to, instead of tri-stating the two signals, mux them together using the tri-state select as the mux select.
Send the two tri-stated signals to two separate output pads, then tie the two pins together externally.