The WCOL bit is set if there is a write collision, I think this is only when using I2C protocol.
From Data sheet:
In SPI mode.
The SSPOV bit is set if a new byte is received while SSPBUF holds previous data.
Data in SSPSR is lost on overflow. In Slave mode, the user must read the SSPBUF, even if only transmitting data, to avoid overflows. In Master mode, the overflow bit is not set, since each operation is initiated by writing to the SSPBUF register.
(Must be cleared in software.)