Pat Harkness, a Canadian (eh?), commented on survivability in that you need a minimum of two routes into a facility and not be painted into a corner when there is a transportation issue with getting access to the EOC. A very good point on survivability and accessibility indeed!
Being close to the centers of government or decision making definitely has its advantages. Being in the basement of the courthouse at least has that going in your favor.
I'll give you two examples that I have personal experience with.
The State of WA EOC when it was being sited had two options. One was close to the capitol, but not on campus, just up the freeway a bit. The other option was on Camp Murray, a National Guard Facility. The one closer to the State Capitol ensured accessibility. The one on Camp Murray had other advantages. It was on a secure site with 24/7 gate guards, it is also part of a larger campus setting and that allowed the budget for the new facility to be trimmed by $4M, which of course was attractive to budget people. It is however at some distance (18 miles?) from the State Capitol and there are bridges to contend with that could fail or be compromised in a larger disaster, earthquake or lahar. The cost and other advantages outweighed the accessibility argument.