When we have made most of the planet uninhabitable, I wonder if we'll be patting ourselves on the back for having made sure that concern for the environment did not override more important issues.
You don't need to knock down or encroach on anything. Just put the tram line down the road, as many other apparently civilised and advanced countries appear to have no problem doing. Traffic restrictions (with encouragement to use the much more suitable A34 and Prince's Parkway corridors) and priority measures can be installed to make sure it runs reasonably fast.
I should have expanded. We seem to have an attitude in this country that we have to find a solution that leaves some at a major disadvantage. So rather than tackle pollution, congestion and social exclusion holistically by improving ALL public transport to allow people to choose not to drive, we have adopted the idea that the principle role of Rail (especially light rail) is to replace Buses, not cars - therefore those that can't access Light Rail (due to remoteness of stops), have to choose between car, taxi or isolation. So, by taking a short-term "populist" solution you are storing up greater long term problems through increased congestion (an electric car still takes up many times the space of a peak hour Euro6/hybrid double-decker) and socio-economic exclusion (can't get to jobs, can't get to shops, can't get to the doctors etc) with all he health implications. Or to put it another way; to reduce lung disease, we'll find a way of increasing bowel cancer (poor food) and stomach cancer (often stress-related).
However, it is worth looking at the two parallel corridors;
Princess Parkway (not Prince's) is a fair distance west of Oxford Road, and is the one corridor in GM with more than 4 peak bph (each way) named in the top 10 pollution hotspots in the county. Not surprisingly, it is very congested, so could hardly take more car traffic.
The A34 is similarly congested, but is slightly better served by bus with 7 off peak bph, rising to nearly 12 in the morning peak. 6+ of these are provided by Stagecoach service 50 which is hybrid operated...............and, off peak at least seems to stick to hybrids more reliably than the 42/43 services on Oxford Road. The downside is that the 50 does not serve Piccadilly. Piccadilly only has the hourly (Arriva) 130, which is apparently much less punctual than it was even a year ago. Shame, as the MRI is actually closer to the A34 than to Wilmslow Road.
So, there is an argument that some buses to Piccadilly should use the A34, but obviously most won't switch. And I suppose for all my musings over the ethos of Students seeing Rail as more environmentally friendly than buses (irrelevant of how they are powered), everyone's principles are challenged by "the bottom line", and the bottom line is that MagicBus is cheaper than any existing or proposed alternative.