I don't have a MacPro 2013 or this Philips display so cannot speak from personal experience but in general you need to enable MST support on the 5K display if it is not already enabled. This maybe under the heading of Displayport 1.2.
If you get this working you may find nothing displays until the Mac has finished booting or before then you get two side by side displays or half a screen. Try unplugging and reconnecting the screen after the Mac has finished booting, this should get the Mac to re-detect it.
The Mac needs to be set to 60Hz but I would hope it would default to this, however check it in preferences.
Yes you will also need to use two connections which go from two Mini Displayport connections on the Mac Pro to the connections on the Philips display. If they only do a Displayport cable then you would get two Mini Displayport to Displayport adapters or buy new cables.
With regards as to whether to use a single Displayport bus or two separate buses on the Mac Pro this will be a matter of trying it and seeing what happens. I could not find any notes from Apple saying one way or the other so there is a possibility it does not matter. If it does here is the Apple article showing which socket is on which bus. See Use multiple displays with your Mac Pro (Late 2013) - Apple Support
For what it's worth it has been possible to connect the Dell 5K screen to a classic Mac Pro with a single Nvidia card and both connections running from that single Nvidia card. To me this suggests it probably would be possible to use the same bus on the Mac Pro 2013. I could not find much about Macs on the Philips site regarding this screen but did notice they specifically list the Nvidia GTX-980 card as being supported in Windows PCs and this card does work at 5K with the Dell in the Classic Mac Pro - not that that helps you much. I also could not find any indication of a specific MST or Displayport settings on the screen so would tend to presume it is on as standard.
Since the Dell UP2715K is now discontinued this Philips screen looks an attractive possible replacement and has the bonus of a built-in webcam and speakers. If you do get it working please let us know.
Overall my recommendation would be to connect it just like the Dell UP2715K.
I did also find an article about using the HP Z27q 5K with a Mac Pro 2013. I suspect this article was written before Apple added official support for this monitor. As per Using 4K displays, 5K displays, and Ultra HD TVs with your Mac - Apple Support
The article I am referring to here - http://www.iclarified.com/49265/how-to-enable-support-for-the-hp-z27q-5k-monitor -in-mac-os-x-yosemite explains how to install a custom display configuration file to enable 5K for the HP screen. My guess is that this is now built-in as standard in newer versions of OS X. My further guess maybe that currently no similar setting exists for the Philips screen and this may be the cause of your problem.
If so the solution would be the same you would need to create and install a similar custom display settings file for the Philips screen. The following website might help you with instructions and a web tool for helping to generate a suitable configuration file. See https://comsysto.github.io/Display-Override-PropertyList-File-Parser-and-Generat or-with-HiDPI-Support-For-Scaled-Resolut…
I would as per the above article find your Vendor and Model ID values and then try generating a file with otherwise similar settings to the HP example file in the iClarified article since that is a 5K display. What should happen is that the Mac will find the Vendor and Model ID from your Philip screen look for the matching display config file and see 5K is to be supported.
To install a custom display config file in El Capitan or Sierra might now require disabling SIP protection.
