HomePNA1.0 (1Mbps) and 2.0 (10Mbps) can be mixed in the same HPNA network, but you may not get the speed that you expect.  The following information (courtesy of NETGEAR) explains:

Although the two technologies (HPNA1.0 & 2.0) can coexist, there are some drawbacks. HPNA2 devices cannot operate at maximum speed when combined with HPNA1 devices.   Whenever, there is a HPNA1 device in the network, the overall network speed will drop to approx. 3 Mbps for the HPNA2 devices, due to the network “overhead” required by the “compatibility” mode.

To put it another way, HPNA 2 devices will communicate with HPNA 1 devices at 1 Mbps, but HPNA 2 devices will communicate with other HPNA 2 devices at 3 Mbps or less. Once the HPNA 1 devices are removed from the network, the HPNA 2 devices will reach their maximum speeds.