OSHA does not require a specific face-to-face exchange of information between the employer and worker. That is because there are lots of ways assignments are made, including through radio communication with the employee in charge, via a written work order, by electronic communication via computer, etc. It can also be provided through training, in a written safety manual, or by written work procedures.
The key here is that the exchange of info has to communicate the necessary information about a particular job in question.