I've got FLAGS! Now, how long do they sit there before AT&T puts in the Fibre?

Nobody here knows as this is a public customer to customer forum only. It could be days, months, or even longer depending on the work order and other factors. I wouldn't hold my breath waiting for the green light.

Digging / boring to deploy fiber would be performed by a local contractor. The larger the neighborhood the longer before all work would be completed.   Generally minimal 60 addresses could be up to 800+ as the PFP sizes support multiple splitters for individual connections.  

It could be a long time before the actual laying of the conduit and running fiber through it begins.  For me it was 3-4 weeks.  That lasted a little over a week for mine and neighboring streets.  Then AT&T crew put the fiber in and the taps and that was done in about another week or so.  Two weeks later, the https://att.com/availability site showed my address as fiber-available, so net 8 weeks.  That's about as fast as I've heard anyone experience, so that's the absolute minimum.  AT&T could decide to put your project on hold at any time for any reason and it just not happen; I've heard of that too. 

Then, too, sometimes it gets put in the database as ready to go, but some engineering problem prevents them from actually hooking you up.

You just won't know how long until you have it installed, I'm sorry to say.

HHmmmm,,,, Ok,,,, I "get" the answers, BUT.  I'm afraid I don't get the point of the installation crew, who ever the heck they really are, going through the trouble of even having a marking crew putting down the markings and the flags.  From what I've read, in Texas after a max of 14 days the flags become obsolete and effectivelly meaningless.  We've already had rain up the wazzoo for 2 days straight.  Folks are out there mowing like crazy right now, sounds like no one is really running the show.  Guess I'll believe it when I can look them in the eye.  

You make a request for marking and you don't know how long it will take to get it marked, you don't know what issues may popup on a job you're trying to get done before the one you just got marked, you have no control over the weather.  An "expired" location has about as much meaning as an expiration date on a bottle of water... the water doesn't instantly turn bad and the underground pipe isn't going to move.