Optical communication is the same way, there is massive bandwidth that isn't being used, so while it might roll out at 1Gbit, it wouldn't' surprise me that in 20 years a x8 stranded fiber network would be well into the Tbit/sec rate.
You don't have to expect breakthroughs to think digging new trenches might be a mistake; all you have to believe is that wireless network performance will continue roughly along the trends it's already been following.
I'd prefer it if us Americans would believe in the former, but unfortunately I think our culture expects the government to do the latter (or nothing at all).
Spending a significant amount of money on something that requires a significant install and maintenance (trenching bedrock, cut lines) when there are potential solutions just around the corner seems to me like bad policy.
I'm sure that there are other, more effective uses the government could put that money towards. Maybe the most efficient and beneficial thing for Boulder would be to not take on more debt, I don't know. Just don't be too quick to assume that all expenses and public works projects are net positives.