The story goes, when the Seahawks drafted DE Bruce Irvin at 15, the Jets backed out of the deal because they no longer felt confident they'd get the edge rusher they wanted. They selected North Carolina DE Quinton Coples at 16, and DeCastro fell to the Steelers at 24 anyway.
The Jets are at 18 now, and with a recent report suggesting the team is looking intently at Texas Tech move TE Jace Amaro at 18, the Steelers have only to float their own "news" they, too, are interested in Amaro at 15, and see if they can create a market for the tight end with the 15th pick.
Trading down would be ideal for the Steelers, a team in need of cornerback and wide receiver help - two of the deepest positions in this draft, but it's debatable whether any of the players at those positions likely to be available would be worth the 15th pick.
The 18th pick would be a different story.
Loosely going off the somewhat antiquated Draft Trade Chart, a reasonable trade would be the teams swapping picks and the Jets giving Pittsburgh the 15th pick in the fourth round (115th overall). The Jets received the fourth pick in the fourth round (104th overall) from Tampa Bay as part of the Darrelle Revis trade, and if they can be sold on the idea the Steelers are going to select him, perhaps Pittsburgh can create a draft-day deal.
The possibility exists the Jets are doing the same thing to a team a few picks behind them, but it's interesting to keep in mind the smokescreens and speculation generated this time of the year.