Key dates that the contract winner (Airband)

I want to know the key dates that the contract winner (Airband) has to complete the work for them to have for filled their contract and give us the tax payer, the payer of the bill the internet coverage that has been contracted and promised.

The contract with Airband for the delivery of the Lot 4 requirements commenced on 28th April 2017. The initial implementation phase of 3 years is contracted to complete on or before 27th April 2020 with a contracted obligation upon the provider to maintain the network for a further 7 years beyond that date until 27th April 2027