Merely having a dedicated phone number and people to answer it does not begin to approach the challenge of an immigration hotline. A correctly developed hotline will handle calls and questions from a target caller archetype, provide timely information to that caller, and, from the administrators point of view, be manageable with reasonable, and not overwhelming effort, and be able to deal with not just a large number of calls, but spikes of calls during emergencies and busy times of day.
Facebook groups for lawyers, and immigration lawyers in particular, are so important that for many immigration law would be impossible without them. This is because the pace of change in immigration law has been so fast the past four years that it requires working together and crowdsourcing information just to have a chance of keeping up. But, Facebook Groups for Lawyers are also bad at maximizing the power of the resources they crowdsource.