Thank you for contacting Ask Extension. Arborvitae are hardy but the extent of damage to the lower portions of the arborvitae will be determined by the presence or absence of buds (growing points). If buds are present, the lower branches will produce new growth in spring. The new growth should be apparent by early summer. The lower portions of the arborvitae will remain bare and likely never develop new growth if no buds are present. I could not see any buds in the pictures, but there is a possibility that they can bud out when it gets warmer. 

Whether they bud out or not, they will never be full like they were. You can interplant other species of shrubs in between the arborvitae to maintain a barrier. If you keep these, you should put up a fence about 18" away from the trees so that deer cannot get to them. Burlap is more for winter damage than to keep deer away. 

Here are brochures to help you for the future. If we can be of further help, please contact us. 

https://yardandgarden.extension.iastate.edu/faq/deer-have-eaten-foliage-bottom-portions-several-arborvitae-will-bare-areas-green-back-spring

https://extension.unh.edu/blog/2019/04/deer-damaged-number-plants-my-garden-over-winter-what-can-i-do-prevent-happening-again