http://forum.mikrotik.com/t/new-features-in-2-9-11/4754/1 indicates at some point support for this was added.
http://forum.mikrotik.com/t/mikrotik-snmp-system-mibs/15951/1 claims it’s the Cisco MIB Chupaka posted, but I cannot get that to work on 4.2 (Solarwind’s Orion Custom MIB Poller reports “Device does not support this OID” when I try to query it.
I’ve emailed support asking if this is still supported, and what the OID is.