time between conditional offer and actual hire

Jumped through my last hoop for a facilities job with BNSF. Over 3 weeks between conditional offer and physical. I have to assume they have reviewed my background check, hair drug test and strength test, it has been 48 hours since my physical which was the last condition.

Questions-
Do they in fact review results as they come in, or do they wait until all the info is in then review all at once?
Whats the experience with the wait time from this point?

I have never encountered so little communication when applying for a job. I haven't had any personal contact with them since the interview, and just the one "congrats on the conditional offer" email from BNSF. All other communication has been scheduling with the individual companies doing their testing.

What you describe sounds pretty normal.

My experience was interview on December 17, conditional offer a couple of days later. I had all my background check, physical, and other stuff finished by New Years. Then I waited and waited. On February 24th I got a call telling me to report for duty on the 28th. So much for the two weeks notice they had assured me I would get! Fortunately my employer at the time was pretty understanding and I still left on good terms.