The prefix ICOM indicates the information cited comes from in-vision commentaries. It can be compared to PCOM, which indicates the podcast commentaries made available during the RTD era, or DCOM, which relates to DVD commentaries. The necessity for separate prefixes is because every Tenth Doctor episode has a podcast commentary, most also have an audio commentary on the DVD (a "DCOM"), and some have an ICOM as well. Thus, the only way of keeping them straight is to use different prefixes.
Please note that Doomsday in fact has two ICOMs, so when citing, the ICOM prefix won't be clear. Recommended language might be "the producers' in-vision commentary on Doomsday" versus "the actors' in-vision commentary on Doomsday".