It's definitely not there. Some people have complained about this when parsing XML files using the .NET CF, but I found out about this yesterday night while trying to custom parse an iso-8859-1 encoded KML file. These files are used by Google Earth to add layers of geographical information on top of the displayed map. The content is regular XML with a specialized syntax that is recognized by the Google Earth application and you can find lots of sources of this type of files. Currently I'm developing a native Virtual Earth map browser for Windows mobile and I want to add the option to read these files and dynamically add the information to the map - that's why I met this issue.
When trying to convert a string using the MultiByteToWideChar API, I got an invalid parameter error when using the iso-8859-1 (28591) code page. A very brief search showed me that this is aknown issue and that, apparently, it's the device manufacturer's decision to include a given code page. Thankfully there seems to be a solution that should solve most of the conversion cases: use the windows-1252 code page.
Now I'm glad that I'm custom-parsing the KML file because I can cheat the encoding section and replace the iso-8859-1 with windows-1252 on-the-fly. I'm not sure I would be so successful if using an automated parser (native or managed). Now the question is: why is iso-8859-1 not there?