The Inquirer reported this information a few days ago and NVIDIA's reference motherboards screenshots published by our colleagues from AnandTech confirm it too. The nForce 5 Intel Edition is in fact the combination of a C19 and MCP55 chip.
The C19 is also included to the nForce 4 Intel Edition and acts as SPP or Northbridge. It supports 800 MHz and 1066 MHz FSB and includes one PCI Express x16 link which is connected to the MCP55 by a HyperTransport link. The MCP55 which is in fact the AMD's nForce 5 acts only as a southbridge and supports 1 PCI-E x16, 4 PCI-E x1, 6 S-ATA, 1 P-ATA, 2 Gigabit networks, 10 USB 2.0 and is compatible with HD audio codecs.
In order to be on schedule, NVIDIA has preferred using a proven technology. The C19 is now more than one year old but this isn't dramatic as the memory controller is very good and offers a comparable level of performance to the Intel i975X. The latter has by the way not much evolved since the 925X released two years ago! Only the i965 and the future SPP NVIDIA C51XE will integrate Core 2 Duo specific optimisations but performance gains will apparently be very low.