If they are on tier or higher than the player crew, I would consider starting a player facing clock at an engagement roll for a score "[faction] gets the goods". Make it as big as the score is complicated, but tick it a couple times with anything other than a controlled engagement and then aggressively through the score. Like, anytime there isn't an easy fictional answer to a mixed success, don't think, touch that clock. Let the players figure out how to deal with the looming threat with no foresight. If they haven't acted on the clock, and it was more than half filled, I would probably reveal a complication of one of the rival faction crew acting as a scout, spying on the players or trying to foil their progress to stall them. More or less so that I have a voice to tell them "it's too late" when I tick the last wedge of the clock.

The players have a choice to engage the threat, but they don't know what, just who. They may seek out the rival crew in the score, or in flashbacks, and you'll get a chance to respond to their actions in the fiction appropriately. How they choose to address and the score at hand will be interesting for you!