With difficulty, yes. The Inuktituk speakers will have an understanding of Inuinnaqtun. There will be big differences in the translation of a word. For example, our languages commissioner in Nunavut is Inuinnaqtun. One of the things she said to me when we hired her was that she was going to have to brush up on her Inuktituk because of the differences, besides brushing up on her French.
When the Inuinnaqtun people are speaking—and from my own personal experience because my wife is Inuk—the Inuktitut speakers have to listen very carefully to what they're saying. That's the same with the Inuinnaqtun speakers too. They all have to listen very carefully to what the Inuktituk speakers are saying, because there are differences in how they interpret a word.