It would depend on the context of the sentence. Example: Their reasons are to be given at a later date. Their reasons would be given at a later date. So yes I’m certain context it can be replaced ☺️

What is the full sentence?

I would say that 'are to be given' is replaced by 'will be given' Their reasons are to be given later. Their reasons will be given later. But it is not really possible to say it works in every situation.

Without having a context, it's impossible to say 100%. However, generally, 'would' and 'are to be' have different meanings, so 'would' probably can't be replaced with 'are to be'. We'd usually use 'are to be' if we're talking about something that is scheduled to happen in the future. Prizes are to be given to the first 50 people who receive the vaccine. Schools are to be given advice on how to protect children before they reopen in September. Starting next month, people entering the country are to be given Covid tests. These are all things that are scheduled to happen in the future. This is the sort of context in which we would use 'are to be given'.