Are the wife's maternal aunts, including her mother, considered foster sisters to the husband if the husband's mother breastfed one of the wife's maternal aunts?

Lactation establishes the same prohibitions as lineage. Thus, the suckled child becomes a son to the wet nurse and her husband. This prohibition is specific to the suckled child himself, not extending to his siblings. Based on this, your maternal aunt who was suckled by your mother is considered your sister through suckling alone. As for your other maternal aunts and your wife's mother, they are not your sisters through suckling unless suckling is established between you from another source. Therefore, your wife is not the daughter of your sister through suckling. It is a condition for lactation to establish prohibition that there be five full, satisfying sucklings.