It may not be as rosy as it look
Earning may not materialise for a few years if everything going according to plan.
There are execution risk in building tower cost can blow out, they may not get the required subscriber, Optus and Telstra won't sit still they have an all out price war for mobile as they have infrastructure in place already
It costly to maintain the tower once you built them etc.. they now have much much higher sunk fix cost.
Telco is not a high return business lot of competitions and high fix cost
Obviously if tpg can lower cost steal customers then they can make a few bucks but the jury is still out on it