The BD v Eng first test will be over before the U-19 tournament. The ODIs don't start until the 7th. I think the consensus is BD needs one player from the U-19 in the squad for the open slot - either batsman or spinner (Aftab, Nafis, Enamul jr are prime candidates).
So the schedule analysis means the selectors have all options open to them:
1. have the U-19 player selected play inthe first test and then go to Pak - hectic but possible
2. Have the U-19 player withdraw from the U-19 team and play the full england series. I don't like this option for damage to the U-19 team as expressed in different thread. Also where the heck is Talha Jubair - teamless?
3. Have all U-19 players available for ODI series as long as BD U-19 don't play in the final on Nov 6th.
So, all options are available. let's wait and see what they do. They'll probably figure playing Mushfiq is the only option.