Can property that has been posted for foreclosure or on which the note has been accelerated be included in the chapter 13 plan?

Yes, as long as the arrearage is to be cured throughout the life of the plan. The debtor is to continue making the regular mortgage payments directly to the lien holder to avoid any post-petition arrearages accruing. It is common for a foreclosure sale to be stopped due to the filing of a chapter 13 case.