There’s a whole McGinn-Nickels spat right now over the deep-bore tunnel, one that has a few more hard numbers than usual. Dominic Holden at Slog has the best rundown of those numbers.
To summarize, Nickels has numbers showing that the surface/transit option costs the City $936m — slightly more than the deep-bore tunnel ($930m plus overruns), because the State would reduce its contribution in accordance with the $700m difference in cost.*
McGinn has the beginnings of a good response here, but its validity depends on three ultimately empirical questions**:
1. To what extent can State gas tax money be diverted to those $936m in costs under the Constitution?
2. Is the “City pays for overruns” thing enforceable or not? I haven’t heard a legal opinion from anyone without a direct stake in the viaduct fight.
3. Could McGinn negotiate a better deal with the State?
Perhaps a legal mind better than mine can answer the first two of these questions. Kerry Murakami of the Post-Globe attempts to answer the third by asking some State legislators.
*Partly because the anticipated $400m from tolling would evaporate.
**Assuming the Nickels numbers aren’t shown to be inaccurate.