Which channel is which?
One of the biggest obstacles in INterOP is that the first responders simply don't know what channels they share with other agencies. The below is a true story:
Years ago, when both Wayne and Oakland County here in Michigan were on analog VHF, two brothers were sheriff's deputies, one for each county. Whenever they were on the same shift, they had a heck of a time getting with each other to co-ordinate where and when to meet somewhere on Eight Mile Road, the divider between the two counties.(yes, Emimim's 8 Mile) When I heard about it, I told their brother who worked with me "Wayne Counties Channel 3 and Oakland Counties Channel 5 are the same frequency". The deputies had no idea that they shared a common freq with a county that shares the same border. After that, they were able to hook up around dinner time no problem.