Does contact with grandparents survive if a child is placed in a children's aid society's care?

Not automatically, but it isn't necessarily lost either. Once a child is in a children's aid society's care, decisions about who the child sees, including grandparents, generally sit with the society and, where the matter is before a court, the child protection court, rather than continuing to be governed only by whatever informal or family court arrangement existed before. A grandparent's existing family court contact order doesn't disappear, but it may not be practically honoured in the same way while the child is in the society's care, since the society controls the child's day-to-day arrangements during that time.

A grandparent who wants contact to continue should raise it directly and promptly with the society, since maintaining a child's connections to extended family, where appropriate and safe, is often something a society will support rather than resist. If the matter is before the child protection court, a grandparent can also ask to have their interest in continued contact considered as part of that proceeding. Because this involves navigating both the family court and child protection systems at once, get legal advice specific to your situation rather than assuming either that contact is guaranteed or that it's automatically lost.