Yes, let me speak to that.
Provinces decide what they will exempt from social assistance or, as many people call it, welfare. That's within their discretion.
For the national child benefit, most provinces reduce their welfare and then reinvest the savings. But they treat the broader national child tax benefit as exempt. So there is certainly no guarantee.
I should point out, however, that now all the provinces have indicated that they will exempt the universal child care benefit from social assistance.