There is someone who puts bus stop notices up on a nightly basis for diversions. Drivers are also told via the ticket machine and staff notices. The road closures are also put on Twitter and the website.As far as getting messages of diversions across to customers it literally could be done very simply like this once you have knowledge of the closure:
Let drivers know
Let depot nearest to road closure know
Draft up diversion on paper
Print how many copies are needed depending on how many bus stops affected
Get anyone available at the depot to go to the stops to put signs up
Doesn't have to be anything fancy but in a business driven by customers from the public, communication and relationships with them need to be spot on. First do lack good customer relations and social media absolutely shows that