SharePoint 2013 - Access data from One site-collection in another (Catalogs and Cross-site publishing)

SharePoint 2013 introduces Cross-site publishing feature by which you can publish and access content across site collections. Cross-site publishing features depend on Catalogs.

Cross-site publishing was designed with some common scenarios in mind, including:

• Share an item list or a page library as a publishing catalog
  
• Consume a catalog from search
  
• Combine cross-site publishing with the variations feature to enable authoring multilingual sites from a common authoring site collection.
   

With Cross-site publishing, for the first time you can design sites that cross SharePoint farms enabling your sites to span the boundary between intranets and the Internet.

Catalogs - You can use catalogs to reuse content across your sites and across the boundary between your intranet sites and Internet sites. A catalog is a list or library that is shared out to search for consumption on publishing sites. You can shares lists as catalogs for content reuse using APIs.

To Add a list or library as Catalog you need to add it to Catalog colletcion.

public void AddCatalogConnection(CatalogConnectionSettings catalogInfo, 
string[] orderedPropertiesForUrlRewrite,
string webUrl, 
string catalogTaxonomyManagedProperty,
bool isManualRule)

How to access content from Catalogs - You can surface content stored in catalogs across site collections by using the Content Search Web Part in SharePoint 2013.

Use the PublishingCatalogUtility API class to retrieve a list of available catalogs, get information about catalogs and their statuses, get information about lists and libraries that can be connected to catalogs, and start or stop sharing catalogs.