This might just add to the confusion, but as soldiers did move around, and the child Margaret was having a conditional baptism, I took a look outside of Quebec.
In the 1871 Census, for Halifax, Nova Scotia, there are many soldier's wives on the same page, one of which was:
Bridget Russell, age 27, born Quebec, Catholic, Irish, married, soldier's wife
Margaret Russell, age 2, born Nova Scotia, Catholic, Irish
Robert Russell, age 2 months (July birth), born Nova Scotia, Catholic, Irish
With them was another soldier's wife named Lilley Ellet, age 23.