I thought you could get a Brand Inspection done upon entering a state that required one as long as you had the other required documentation and proof of ownership? A friend that moved out to Wyoming had to get one right after she crossed the state lines because she came from a state that didn't have brand inspectors so its was pretty much impossible to already have a brand inspection in hand before entering the state.
As I understand it and I may be totally wrong, every states requirements are different, but you need to follow the requirements of state you are coming from. Since we were coming from NV into CA, I must have a NV brand inspection/transportation permit.
The OP is coming from MT so she must follow the laws of MT brand inspection no matter if Idaho, Oregon or CA ask for it or not. If any of the states she will be travelling through requires a brand inspection and they ask to see one, she will need her MT one, not a brand inspection for the state she happens to be traveling through.
Once she moves to CA and travels she will have to follow CA inspection laws.
In your friends case that would be correct, again from how I understand it, since she came from a state that doesn't require a brand inspection or doesn't have a livestock dept. WY required her to have one to travel within the state and they obviously enforced it.
Some states are stricter about it than others. NV is strict and in the eastern part of the state they will pull you over and check.
Coming into CA over I80 they used to pull in all the hay trucks for hay inspection and you had to get stamped, but now they wave them all through(except for weight) and they pull in(at the bug check) all the pickup and trailers hauling livestock and you must show all your paperwork plus write down the exact address you are traveling to with your phone number.