I've found it really depends on the builder and the market. In Delaware I was offered nothing that wasn't in their options book. I finally got them to agree to a 4 inch chase (PVC) basement to attic on the threat of walking away from the project.
In Oklahoma, they gave me anything I wanted including access to put whatever I wanted in as long as the wire was properly rated for in-wall. Hell they bent over backwards on the specs for the Home Theater.
In Michigan, again I am up against an unmoveable wall. No access, nothing unless its out of the options book (and there is nothing in the options book except a stock alarm) and absolutely no changes post final options selection. These guys do LEAN+ building process, so the place is built in 3 months, changes screw them up I guess....
The main differences between the previous experiences was the OK guy was a custom builder. He had a bunch of plan books, had you pick somthing smaller than what you wanted then modified the design to fit your needs. He came in way under budget too. Both of the others are large regional builders. They only know how to make houses in their current plan books with no mods. They likely buy all the material in bulk and changes screw that up so they are unwilling to bend. They get enough customers (even in these times) that if you don't want what they offer, they could care less.
If it were up to me I would never buy a house from one of them again, but the wife and the wallet play into the decision as well so for this project I am stuck. I will do what I can with wireless and retrofit as well as access I can get from the unfinished basement. Its not the last house we will build and we likely won't be in it more than 5 years so not too worried that its not my dream install.