A great way of finding out more about system tables is to look at the system stored procedures in the master database, whenever I need to find out something about the db metadata that isnt commonly known this is the place to start. sp_help for example is a great place to look for the the things mentioned in the article.

btw the I think the identity column is identified by (status & 128) = 128 as its a bitwise column.

If you need to look at undocumented functionality trace while doing what you want to do in enterprise manager then take a closer look at the releavant sps, obviously be cautious about using unsupported system sps, columns etc!