The cost savings of "real" Bus Rapid Transit over rail, especially factoring in the cost of regular bus replacement, aren't even that great, but the more important thing is that BRT projects inevitably get watered down from the moment planning begins. There are numerous ways to cut costs, and as they snip snip snip pretty soon you're just left with "a bus." Nothing wrong with buses! But they aren't BRT.
One of the main disagreements between the committee and representatives from MCDOT was over a change to the BRT U.S. 29 plan to have the bus lane double as a high-occupancy vehicle lane.