We have 2 site collections SiteA & SiteB. and inside siteA we have 2 document libraries DL1 & DL2. Inside DL1 we have folders and files with unique permissions. now if we use the MoveTo option to move the folders from DL1 to DL2 the folders' & files' permissions will be preserved which is great. but if we move the folders from SiteA to SiteB then the folders' & files' permissions will be lost. so can anyone advice why this is happening? and is there a way to preserve the permissions when moving folders and files across sites?
Its probably losing permissions because user Ids and groups are different between site collections. Losing the permissions is possibly a design decision I would say. I don't know of an out-of-the-box way to move items between site collections, but this seems something you could achieve with a custom solution.