Booger,
Excellent question! This used to be the way they all worked as many insurance claims of all kinds still do. You would pay the bill and them submit it to the insurer. But times have changed with travel insurance as with most things.
Since this is not an insurance focused forum, I will give some basic info and links to more detailed travel insurance sources. We are in no way supporting or endorsing any of these companies, just providing links to how travel insurance works. I googled "how medical travel insurance works?"
All small costs, such as doctor visits, x-rays, mending a broken ankle or general vague illness requiring a doctor visit would all be paid in advance (out of pocket expense) and then the receipts sent to the insurer when you get back home. But for long stays, or very expensive services (medical evac), in the last few years several travel insurance companies offer "primary" coverage, which the hospital or med evac service will work with the insurer directly with no out of pocket expenses.
A travel info based site states that some companies "now offer comprehensive packages that serve as your primary coverage; they’ll take care of your expenses regardless of what other insurance you might have (for instance, if you have health insurance through your job). That means they pay first and don’t ask questions about your other insurance. This can be a real plus if you want to avoid out-of-pocket expenses."
And "With medical coverage, you may be able to arrange to have expensive hospital or doctor bills paid directly....you can also purchase primary coverage, which will take care of your costs up to a certain amount. In emergency situations involving costly procedures or overnight stays, the hospital will typically work directly with your travel-insurance carrier on billing..."
https://www.ricksteves.com/travel-ti...avel-insurance
In all cases, your travel insurer should be contacted asap regarding what is covered and what to do regarding the plan you purchased.
And from another source, "Emergency Medical Evacuation insurance provides coverage for medically necessary evacuation and transportation to medical facilities. These costs can easily reach $10,000 out of pocket if you don't have coverage."
http://www.investopedia.com/articles...-insurance.asp
Costs vary greatly depending on what is covered, your age and any pre-existing conditions. Take your time to compare the different companies and the plans they offer to find what is best for you.