"Permitting or causing distress" is the criminal offence in the PCA Act. Have you considered that there are two ways to relieve distress?
One way to relieve distress is to kill the distressed. That certainly protects one from being charged with cruelty under the PCA Act.
The other way is to treat the cause of the distress.
No-kill rescuers won't kill to relieve an animal's distress, not unless the condition truly is unrelievable. Instead they do the best they can with small budgets to get the vet care that relieves the distress or they provide palliative care to animals with terminal illnesses, just as truly loving pet guardians do. These small groups keep thousands of animals out of SPCAs where many could be killed.
Contrary to what one may assume about the SPCA "working with other rescue groups" many no-kill rescue groups in BC live in dread of the SPCA.
In spite of a rescuers' animals being far happier than animals in SPCA physical and mental illness-causing facilites, if there is any illness, even if being treated, the SPCA can and has stormed in with RCMP and seized the animals, killing many of those happy animals, even animals who are being medicated and under veterinary care.