are subject to a few outside influences such as weather, dirt build up on insulators ect. So an exact calculation is not practical.
The line is built using best practices for clearance from ground and green growth knowing that losses will be within designed limits for the length of the line. The true efficiency is calculated at first operation. Remember .1% extra loss is a lot of dollars.
The line is not allowed to deviate far from its as built efficiency before maintinance crews go to work.

In use changes in line loss are monitored and used to determine need for maintinance. Given a knowledge of local conditions even the type of maintinance needed can often be determined ( cut back green growth or clean insulators or check corrosion in splices)

The use of aluminum would not necessarily increase resistive line loss as you just adjust the conductor size to compensate.

The reduction in tower count would reduce the leakage loss through dirt on insulators.

With fewer towers they can be higher for the same total tower cost
giving better separation and allowing the use of higher transmission voltages meaning either lower amps or more capacity.
Terry