Searching on EF for FI 615, it changes from a 75T to a 76W on April 15.

I believe the 75T is their 757-300, as coach goes all the way to row 41 in the seat map for 75T flights. EF normally shows FI flights as a 75W (752), where coach ends with row 34.

The seat map for the 76W shows Saga as rows 1-5, with 2-1-2 seating, then EC in rows 6-8 with 2-2-2, and then coach in rows 9-40, with 2-3-2 seating.

But this could all change, depending on where the a/c comes from. As mentioned by Braniff, FI puts newly acquired a/c into service when they get them, even if in a different configuration.

This is the seat map for the parent company's 767s, which is very different:

http://www.loftleidir.com/fleet/detail/item467201