There are a couple of possibilities here...
Our database shows 3 individual trunk systems in your county
Wayne County, Michigan (MI) Scanner Frequencies and Radio Frequency Reference
There's a news item on the Wayne system that this system was to shut down by Jan 2014, and move to MPSCS. None of the 3 systems shown have indications that they rebanded, and in fact, the Downriver system, along with MPSCS, don't need any custom tables for rebanding since they're already fully digital. So if Wayne has shut their system down, you need to reprogram for MPSCS
If the Wayne system is still active, and has truly rebanded, not only do you need to add the custom table, you must reduce all the frequencies you've programmed by 15 Mhz. Unfortunately no one has added the rebanded message to that system in the db, so you're going to have to do it manually by fixing the frequencies in Win96 then reloading.
Another possibility is that the Wayne system is not fully rebanded yet. In this case, you'd need both the pre and post rebanded frequencies in different banks, with the same talkgroups. It's not uncommon for a system to run both sets while the frequencies are being migrated.
Either is a possibility, and you need a Michigan scannist to answer it. You might want to post a question on our Michigan forum to see what Wayne is doing (assuming no one from that area answers here).
Michigan Radio Discussion Forum - The RadioReference.com Forums
Mike