I have check with the Army officer there and also local people that tunnel is only open in Winter season and other days this is not fixed that tunnel will open for the week or not, they can close tunnel for any of the week for work and you cannot hold your stay there just waiting for tunnel.
Yes with a special arrangement from any of the Army officer they can arrange your pass from tunnel but matter how many of us know any Army officer around, I have seen 1000 of vehicle passing from lowari pass with world most dangerous pass.
Tunnel is about to open for public in 2018 as said by FC deployed there but who knows this is Pakistan where completion date does not matter.