Speaking at the CommsDay Summit in Sydney, McInerney underlined the importance of the OSS layer in supporting Telstra's aims at the business support systems (BSS) level, which is primarily concerned with customer service.
The OSS and BSS systems are the software platforms that underpin Telstra's ongoing network transformation project.
"The quality of data in the BSS system is driven by the quality of data in the OSS layer," McInerney said.
"For Telstra, the next 18 months is critical from an OSS perspective [because] it's when the rubber hits the road, and a large part of the Australian marketplace is helping us get up to speed."
Telstra is using services partners including Accenture, Infosys, EDS and IBM to deploy and tweak product from Oracle, Comverse, Amdocs, Sun, EMC, Symantec and others.
McInerney praised the technology partners working to implement OSS changes.
"I always speak of the quality of participants on the Australian side who have to get this stuff done," he said.
Although he admitted that more time could have been given to technology partners on the project, he then said he would be looking for partners to "step up" to enable the OSS to handle more complex builds.
"It's the most difficult thing to solve," he said.
"The OSS lends itself very easily to simple products. It's hard to avoid going down a custom build path for more complex products but we'll be putting some pressure on partners to step up [to enable us to do that]."
McInerney also said the telco hadn't focused enough time on simplification of its legacy environment, despite one of the early requirements of the overhaul being to slim down its 1,250-plus existing OSS systems.
"Every program of this size has things you'd like to do again," he said.
"We didn't do enough simplification in the first place. We spent a lot of time replicating legacy systems in the new world whereas if we'd spent more time we could have taken some of them out from a build perspective. Testing 40 years of legacy systems is extremely difficult to do.
He advised: "Simplify as much as you can in the first six months - because if you don't simplify it you're going to have to test it, and you don't want to have to spend months trying to test legacy systems as they pull through."