By following the description below, the SPI Interface is re-enabled.

It's not possible to use the debugWIRE interface if the lockbits on the target AVR are programmed. Always be sure that the lockbits are cleared before programming the DWEN fuse and never set the lockbits while the DWEN fuse is programmed. If both the debugWIRE enable fuse (DWEN) and lockbits are set, one can use High Voltage Programming to do a chip erase, hence clear the lockbits. When the lockbits are cleared the debugWIRE interface will be re-enabled.

The SPI Interface is only capable of reading fuses, signature and do a chip erase when the DWEN fuse is unprogrammed.