That's nothing to do with Bresnan scoring 90 against them, as you have said yourself they have Shakib and Mortaza, Mahamudullah is also handy in home conditions.
Either way this is neither here nor there, I've seen enough from Bresnan in a year of international cricket to suggest that while he will never be a world class quick bowler, he is more than useful to hold an end up and frustrate batsmen. Finn, Broad and Anderson can all be quite expensive if they don't hit their straps (Anderson less so recently), so someone like Bresnan could be very handy for England in years to come. He's a more than capable batsman aswell which just adds to the case for his selection.
Swann and Jimmy have often been referred to as bowlers who can hold up an end. In a 4 man attack, you actually need two or three bowlers who can take wickets as well