Turkish minister for transportation and infrastructure C.Turhan say, tender for BİT (Büyük İstanbul Tüneli - grand istanbul tunnel) is planned for 2020. Minister say they plan to do it with Build-Operate-Transfer (BOT) model. Preliminary study for BİT recent completed.

Note that minister's most talk was about in general what they achieve. BİT was only a small part of ministers talk.

https://www.dunya.com/ekonomi/bakan-turhan-buyuk-istanbul-tuneli-projesi-ihalesi-bu-yil-planlaniyor-haberi-461786