How does changing plans work if it happens in the middle of ongoing treatment?

I’m honestly a bit embarrassed that as an older adult I don’t know this, but for the first time I’ve had to change my insurance plan soon after having surgery (cervical fusions) that is requiring multiple follow-up visits and a several months of therapy. (And I had a second unrelated surgery done at the same time, but there’s no on-going treatment for that, at least so far. Knock on wood. 😛 )

Both my current plan and the one going into effect in January is through Anthem Blue Cross, and if it matters, the current one is a PPO and the new plan will be an EPO. (The Ortho is still in network on the new plan, so no concerns there.)

So how does it work as far seeing the ortho, followup testing, prescriptions, and approving therapy? Does the new plan take into account my recent surgery and what is needed, or will there be pushback and I should expect to have to jump through hoops to get ongoing care approved again?

(And apologies if my question isn’t clear as I’m having a hard time articulating what my fears/concerns are.)