Don't know where you are located, but in Ohio (southern) my club calf bred cows are all stalled when due. I like to have them where I have quick access to a chute if needed, easy access to the calf for any issues (e.g., nursing), and to easily give the first shots and a dose of pro-biotic I like to use. I also use a camera system to monitor them inside. Finally, in winter I can prevent frostbitten ears.
If you have them bred commercial or maternal and lower risk for calving issues they can calve outside.. I had pure bred limousin for several years and many calves delivered outside in very cold conditions.
To my mind the calves I breed for today are just too valuable to leave much to chance. With ET calves I would personally put them inside to calve if you have that option.