FYI,
I just got back from Bangladesh - absolutely fascinating and amazing country - loved it and I will surely return; hopefully soon!!!
I was told that one no longer needs a change of route permit - I had entered the country by land from India via Bhomra border crossing (not Benapole which is an entirely different story) and left by air from Zia. I did not get the change of route permit and had no problems leaving the country - the immigration officer was surprised I came through Bhomra though - like I said that is another fun story :-)
Anyone going - I am envious - Bangladesh is such a wonderful place to be!
Have fun...