Central Region manager Ros Alsford said the team wasn't sure how the pair ended up in the wrecker's yard.
"Mitsi and Lancer could have become separated from their mum and lost. Either way they are incredibly lucky to be alive."
Alsford said the duo were healthy and were being given around the clock care from a foster family.
"This is one of the more shocking stories of survival that we've seen. We are so grateful Mitsi and Lancer were found and that SPCA can help them on their road to recovery," Alsford said.
"Mitsi and Lancer are only 3-weeks-old, but already life has been quite a ride for them. At this age they are particularly vulnerable to disease, starvation and injury."
The kittens would still need several weeks of care before being big enough to be desexed and adopted.