Scalfaro, Napolitano e Montalcini have strong relationships with the Prodi coalition, so their vote (at least for the initial government creation) will most certainly be casted with the Union. Cossiga is kind of a crazy horse, so you can't really say, but he fell out with Berlusconi a while ago. Andreotti could ask for something in return for his vote, and where he votes Colombo will probably follow. I have no idea about Pininfarina (didn't even know he was a senator!).