I can't see anything like the Boston Big Dig happening in Birmingham in the foreseeable future, simply because getting money from the government to fund infrastructure projects of this magnitude is nigh impossible, fortunately, we already have the Queensway Tunnels running underneath the city centre which diverts traffic underneath the city instead of the busy streets above.
High Speed Rail 2 will be a massive opportunity for the city, where huge areas around Curzon Street HS2 railway Station in Digbeth will be redeveloped, a government Regeneration Agency has already been set up.