UPDATE!
After some time and effort, I have learned a few things about programming the Signalling Option of the MT1000. It seems that I am not alone in experiencing frustration when attempting to program these special front covers for this radio.
http://batboard.batlabs.com/viewtopic.php?t=17930
Serial Bus Access 006 corresponds to "Retransmission NAK'ed" according to the RSS User's Guide for R03.01.02. This however, did not help me very much, other than tell me that the radio did *not* like what I was trying to do.
The cover that I have been attempting to program is an NTN6009C. This is a "Man Down" cover with a board-mounted mercury switch and an orange button on it's raised top. According to the Option Chart contained within the Service Manual, this cover is only available on VHF or UHF 8-channel rotary radios, both low and high power models. Of course, I hade mine slapped on a 16 Channel (H34GCU7100CN) radio.
Once the cover was attatched to an 8 Channel (H34GCU7180AN) Radio, the front cover was successfully programmed. After the programmer writes to the front cover, it instructs the user to turn the radio off, and then back on to verify proper operation. This is probably to re-initialize all of the newly programmed options in the front cover.
Interestingly enough, other MDC covers such as the NTN5456 (no emergency button) and NTN5457 (emergency button on raised top) are available with every model MT1000 listed on the option chart.
I have still been able to add channels in the RSS and write them to the 8 channel codeplug with this front cover on the radio. So 16 channels and Man Down is achievable with an 8 channel codeplug. It looks like this cover will be unusable on any 16 channel codeplug, any lowband radio, and any display radio.
). Also, the software prompts me to turn the radio off and then back on before programming the front cover. Error 006 comes up whether I turn it off and on or do nothing and attempt the write.