I can't quote it directly, since I no longer have the book, but the Enterprise D technical manual, which I bought just after seeing Generations, and was published around season 5 or so, specifically states that no Federation starship uses static shield frequencies anymore, meaning what the Bird of Prey did should have been technically impossible at the time, on top of everything else. Still, it did get us the Sovereign class Enterprise, so...

TRB

(who thought the triple-nacelled, giant phaser cannon equipped Enterprise-D from the final episode had some potential, at least)

"You are... what you do... when it counts." -The Masao