When the monorail from Transportation & Ticket Center to Epcot is running, there will be no bus duplicating that route.
If you took the Express monorail from Magic Kingdom, you would walk across the platform at TTC to board the Epcot monorail. Going in the other direction from Epcot to MK, or if you used the Resort monorail in either direction, you would have to go down one ramp and up another at the TTC to make the transfer.