The following is taken from a Zenit news item posted July 7, 2004. The question was answered by Father Edward McNamara of the Pontifical University. It provides further confirmation that the homiletic practices in the DOR appear to be an aberration, not the norm. (Thanks to Rich Leonardi for finding this).

Q: After the Gospel reading, sometimes our priest sits in the congregation and a lay minister gets up to give a reflection. When I questioned this practice with our bishop’s office, I was told (not by the bishop) that as long as the priest gives a homily, whose duration could be one minute, the lay ministers can give the “reflection.” Is this true?

A…Therefore it is quite clear that the answer you received from the chancery office (which may have been before the publication of this new instruction[Redemptionis Sacramentum]) is now quite incorrect. Before this clarification was published it was considered possible that a bishop could authorize a layperson to read a prepared text after the homily on some special occasions. This was always seen as an exception and never a habitual practice. The reason given in the document for this disposition is that the homily is part of the liturgy itself. As such it is a sacred action and only a sacred minister may carry it out.