It will build new coverage at 50 sites including the Mornington Peninsula as well as roam on parts of Telstra's 850MHz network from the second quarter of 2009.
But a Telstra spokesman indicated yesterday that Hutchison customers would not receive equivalent speeds on the network as Telstra users.
"Once the roaming arrangement commences next year Telstra will maintain its market leading speeds and coverage," he said.
A Hutchison spokeswoman said 3 customers would receive the fastest speeds available.
Hutchison booked an $85.4 million net loss for the six months to June 30, from a $197.3 million loss a year earlier.
It posted a loss before interest and tax of $31.1 million, compared with an $88 million loss previously.
Revenue was up 23.7 per cent to $760.9 million.
During the period subscriber numbers rose 28.7 per cent to 1.81 million.
Ovum analyst Nathan Burley said Hutchison's 3G roaming deal with Telstra would ensure the telco remained competitive.
"Although 3 was the initial driver of 3G adoption in Australia, in the coming year it was in danger of being left behind," he said.
"Telstra's game-changing Next G network has taken 3G competition to a new level, forcing competitors to respond."
Hutchison shares fell 2c to 11 yesterday. Telstra shares fell 2c to $4.36.