It could be a cross border violation by mistake, there are no borders in the air, no LOC marking helps at 30,000ft. GPS co-ordinates and flight path did, but there is always margin of error while operating close to the border. I'm not advocating NATO here but it looks like a routine matter, only reported in news as something serious.
It seems that Pakistan and NATO/US has agreed upon something regarding NATO operations near Pakistani border, which were halted after Salala episode. On the eastern side, the ROE are different as compare to western border; a scramble has been called on whenever any Indian aircraft comes near eastern border, this is clearly not the case on western border.
Now what lessons Pakistan has learned from Salala? I don't think any.
What changes we did in our foreign policy after Salala? I haven't seen much implementation, other than statements in the press. Drone strikes, supply line have fairly gone down but overall the situation is same. Before Salala, PAF was never allowed to interfere on the western side, and may be things are pretty much the same now.