If some of the expats have Brit citizenship then there is no excuse for supporting any team over Eng (their national side).
If some English bloke came to Ind and took up Indian citizenship, and then in an Ind vs Eng fixture he started to cheer for Eng, I would not exactly be welcoming that attitude.
While its good that Ind get so much support, but if they are Brit nationals, then they should be supporting Eng, not Ind or Pakistan.
Also if Moenn Ali is English, then the only team he belongs in is England. I don't think that if he changed his nationality, and started playing for India (I know he would go Pakistan, but suppose he did), I don't know if I would welcome him.
Recently I read about Michael Chopra (who is going to take part in the ISL) former Newcastle United player, wanting to take up Indian nationality, to be able to play Int'l Football, I thought I would not exactly be thrilled about it. He has been a brit all his life, so why play for India now.
Same in cricket. Moenn Ali is English and there is only one team where he belongs. Those who booed him for that are stupid.