No, not in the way that SPI works. However with a bit of hardware you can do it. For example you can use a CD4066 to switch between devices. Another option is to use a PIC with two usarts. It all depends....

Perhaps you can use the USART for the RN-171, use SHIFTIN/SHIFTOUT (or the MSSP module) for the MCP2515 and use SERIN/SEROUT for the RF-module. It all depends....

The speed of the bit-banged SPI (ie SHIFTOUT/SHIFTON) commands depends on the osciallator. The manual says 50kHz dependant on oscillator (I suspect 4MHz) and that the active state is held to a minimum of 2us. I interpret that as no matter how fast the PIC runs the active state will always be 2us, assuming that the clock is symetric that means 4us per bit or max 250kHz. I think that in reallity it'll be quite a bit less than that. So, if you're comparing the USART to bit-banged SPI I'd say it's likely that the using the USART will be faster and because receving and transmitting is handled by hardware the PIC can do other things - if used properly.

SHIFTIN/SHIFTOUT can be used on any pins of the PIC - not just the SDI/SDO pins.
Using the MSSP module to do "hardware SPI" requires the use of the SDI/SDO pins since that is the pins to which the MSSP module is connected. SHIFTIN/SHIFTOUT does not use the MSSP module.
SERIN/SEROUT can be used on any pins of the PIC - not just the TX/RX pins.
Using the USART to do "hardware asynchronous" communications requires the use of the TX/RX pins since that is the pins to which the USART module is connected. SERIN/SEROUT does not use the USART. HSERIN/HSEROUT does.