Yes I've booked DME-IKT and IKT-DME using avios, using ba.com with no problem at all. As I recall, there was loads of availability in both cabins.
You won't be able to book a cash fare to IKT using ba.com as the system doesn't recognise IKT (as no codeshares on the route, S7 codes only). You can only through-book to S7 destinations which are BA codeshare destinations.
You can certainly plug in IKT to book using avios (if seats available).