how Escape Characters vs metacharacters are handled by the complier?

To be honest, this depends on the implementation. A good general introduction to the kind of algorithms used by regular expression parsers can be found in Mastering Regular Expressions[^] by Jeffrey Friedl. If you are serious about regular expressions then you should have this book.

As to how a regex engine handles things in practice, look at the code for Boost.Regex[^]. The code is freely available.