The move came as a swift reaction to the revelation that the Frenchman is to join DJR Team Penske for next season following 17 years as technical director at Triple Eight.
Data engineer McGregor was swiftly promoted into the race engineer role having already been earmarked to take over the position for 2017.
The pair struggled through the early part of the weekend, turning 21st and 13th place grid slots into 16th and 15th place finishes on Saturday.
With Scott McLaughlin rapidly closing down the points gap, Lowndes managed seventh and ninth in the Sunday qualifying sessions before driving through to fourth and sixth place finishes.
Lowndes now holds a 21 point advantage over McLaughlin heading into the Sydney finale, where 300 points are still available.
The three-time champion commended McGregor for the recovery, noting his distinctly different style to the excitable Lacroix.
“There's no doubt that it was always going to be a bit of a tough start to the weekend after the reshuffle,” Lowndes told Speedcafe.com.
“Irish (McGregor) had a little bit of a taste of it on the Gold Coast but this obviously caught us by surprise and he's been thrown in.
“But he did a great job. Even though we were running at the back of the field on Saturday, he was very calm with his calls and on the radio.
“I think that helped everyone in the garage. He wasn't stressed, which was very different weekend to what we normally have.
“He could have had the attitude going into Sunday that it'd been a disaster because of him, but he didn't have that.
“I was a little concerned that he'd lose a bit of belief in himself and think he wasn't up to the mark, but Sunday showed he made clear decisions.
“It was a slow start but we bounced back well which we needed to do to keep Scotty at bay.
“Scotty will be quick at Homebush, no doubt, but now that we've had a meeting under our belt as a team I think Irish is a lot happier with the progress of the car was and what changes he's made.
“We'll go to Homebush a lot more confident now having this meeting out of the way.”
“It was disappointing, more for Roland because Ludo has been part of the team's DNA for almost 20 years, so I think it affected Roland more than anyone,” he said.
“But we all move around in this industry. It's not surprising, but it's just the timing and how it was done.
“Penske will be a force to be reckoned with next year, but we always knew that once they could gel their team around two drivers they'd move forward.
“They've got good resources so I'm not surprised that they were quick at Pukekohe and I'd only expect them to be stronger next year.”
Lowndes has finished in the championship's top four every year since he joined Triple Eight in 2005, but remains without a Supercars title since 1999.
Although again falling short of the ultimate prize, Lowndes says the result will be a case of target achieved in the first season for Triple Eight's third entry.
“For us when we started the year we had expectations of being in the top five,” he said.
“When we got to third mid-season the focus changed to trying to maintain that position.
“We've had over the last couple of meetings challenges from Frosty (Mark Winterbottom), Will (Davison) and now Scotty.
“We've managed to hold them off so far, but it would be satisfying to finish third as a new entry.
“We share with Triple Eight, but for us to come together as a one-car team it'd be satisfying to be third.
“Roland said he'd never expand to three cars, so to do it and continue our winning ways would be very satisfying for him particularly.”