Find out as much as you can about your city's regulations. In Madison, WI if your conduit is 3" or larger the city can take ownership of it if they want with zero compensation for the cost you spent to build it out. They will reuse it for utilities, traffic lights, etc. You can still use it, but they own it.
This is why you get an agreement with the city to share their conduit and help each other out where possible. Not sure of the political climate there, but getting on their good side will save you money and time.
