Today I committed my recurrence work in evolution-exchange along with other conduit patches. Now, evolution-conduits can sync against exchange and groupwise (needs testing) accounts.
Following links will take you to those committed changes:
1) Calendar conduit
2) Todo conduit
3) Addressbook conduit
4) Recurrence fix in evolution-exchange
Now, that Eureka thing. Yes, the bug was in exchange-calendar code that reads events from the server. According to MSDN, events have some specific property that has values from 0 - 4, which represents events with master object, without master object, detached instances etc. Evolution-exchange was always querying for events with codes 0 and 1, which made the message not to appear in evolution as it didn't even fetch. Chen fixed this thing today.