When accessing the webdav mounted folder /Volumes/[folder name], a file moved to this folder ends up having permissions 700 or rwx------. Is there a way to retain file permissions when files are added in this folder?
Unfortunately there isn’t. WebDAV does not have a concept of file permissions.
A WebDAV client could implement means to store that information. I do not know of a client which does this. Even in that case permissions would most probably not work cross-system.