They mention YTZ-BOS-GCM as a future connection on anothera.
Porter is going to need a 5:30am or 6am weekend departure for that weekly BOS-GCM flight which departs at 9.
In the morning the two Dominican red-eyes arrive in BOS around 7:10 ish as well so you could have 370 people arriving in the customs before 7:30 and you could have a fair amount of non-residents at that time. I don't know how many CBP stations are open for non-residents at that time.
No mention of EWR connections in the article below but it has the timeline for when certain routes will be available.
http://www.newswire.ca/en/story/1424...line-agreement