That package is part of the source code but not part of the binary. It looks like you have to build it manually from the source (it is in the migration directory, which is not compiled as part of the build for the portal) and then include the jar in your archive.
I had read that IPC was not working with 2.4.
should have been solve for the 2.4GA.
but not sure : look at the JIRA.
you can also use IPC by message exchange, using the Michelle Osmond librairy.
search in the forum for "IPC" and "Michelle Osmond"