The Reaper IFF broadcasting the Normandy's location to the Collectors. He offered this up as a plot hole because how could a piece of technology from a derelict Reaper thousands of years old signal the Collectors? How would the Collectors know what to look for? How would they have known to set that trap all that time ago etc etc...

Well, maybe it was not signalling them directly but rather just sending out a general reaper-tech signal. Since the Collectors are currently using Reaper technology, hell they're even communicating with a Reaper, so I imagine it would be a relatively easy thing for them to detect. Perhaps that simply detected this new reaper-tech based signal and, knowing the Normandy was moving in opposition against them and the Reaper threat, put two and two together.

Pure speculation on my part, sure, but it makes sense when you think about it. I think that Bioware can be forgiven for not feeling like they had to explain every single occurrence in minute detail.

they would need some form of land/planet based Reaper for rounding up conquered species etc. Indoctrination(sp) is very effective, but I think the Reapers are too intelligent/methodological to rely on that and a massive space fleet for total Galactic domination/culling.