I do not work across state lines . . I work in two different states on two different sides of the country (Pennsylvania and California). I took classes in both states and took the state exam in both states. I live part time in both states. I am not (and cannot . . .no reciprocity) carry one license over to the other. I hold a completely separate real estate license for each state. Because my broker in PA does not exist in CA, my CA real estate license is not with the same broker that my PA real estate license is with. Both brokers are aware of my holding a license with a different broker in the other state.
However, I think your question is very interesting and I would think that if your two brokers are in direct competition with each other in the same general market areas (ie PA, NJ, NY), then I would think this might ruffle some feathers. I'm curious for more answers on this.