Thanks to Bryanzane and OmarMoreno18 for picking up on this while I was out.
This is a weird trade. At best, it's harmless; at worst, it's potentially a really bad idea. Unlike Don Kelly, who's expected to be designated for assignment to make roster space, Izturis is useful - he's a good defensive shortstop and he should be better than average at second and third, too. Unfortunately, he hits even worse than Jack Wilson does. If the PTBNL isn't a prospect and if the Cubs are eating most of Izturis' salary, and if Jim Tracy doesn't still believe Izturis is a starter, this is potentially harmless.
If the PTBNL is a prospect, or if the Pirates are taking on a bunch of salary in this deal, or if they're seriously going to give Izturis a lot of playing time, then it's a silly move. If they felt they needed a utility infielder that badly with Jose Bautista hurt, they could've easily just called up Brian Bixler or Yurendell DeCaster, both of whom would be cheap and possibly better than Izturis anyway.
Dave Littlefield has said this trade doesn't suggest that the Pirates are going to trade Jack Wilson, and I'm inclined to believe him. Izturis has a $5.85 million option for 2008, and I don't think there's any way the Pirates will pay that. So this deal is for 2007, and the Pirates didn't make this trade in order to have a shortstop for 2008. Maybe they're thinking about trading Wilson and wanted a rental for the rest of the season just in case - think of the way they acquired the utterly pointless Jose Hernandez when they dealt Aramis Ramirez - but I doubt it. They'd probably - well, hopefully - just go with Bixler if they needed a starter.
In any case, this trade has no chance of really helping the Pirates, and with Izturis' former Dodgers manager Tracy deciding how he'll be used, there's cause for concern here.
UPDATE: ESPN reports the Cubs are sending the Pirates about $1.4 million. Their player card says his 2007 salary is $4.25 million and the season's a bit more than half over, so the Pirates will pay about $500,000 for him the rest of the year plus a $300,000 buyout at the end of the year, versus the $125,000-150,000 they would have paid for Kelly. Maybe that's not the best use of $650,000, but it isn't really worth worrying about, either.