Digital interconnects are supposed to be interconnects with a 75 Ohm characteristic impedance. The catch is you can't get that with an RCA jack, it isn't physically possible. Bryston uses a 75 Ohm BNC connector just for this reason. There is a decent chance the digital cable will have too much capacitance.
Cartridges don't care about the characteristic impedance of the cable but they are sensitive to capacitance, which loads the cartridge. The cartridge manufacturer / datasheet will tell you the needed capacitance to load it, of which the cable is part of that and the rest of it is in the preamp / step up input.
Moving coil cartridges typically use low impedance inputs on the preamp or step up device. Inductance in the interconnect has more affect on the sound when faced with a low impedance than a high impedance. So, the preferred cable for a MC setup should have low inductance.
So, you could call Blue Jeans back and find out if they have a unique very low capacitance / low inductance cable for MC phono cartridges. The concept here it is easy to add capacitance to properly load a cartridge but one cannot remove capacitance if the cable has too much. If you opt not to go the Blue Jeans approach, I suggest you find the lowest capacitance cable out there with a good dielectric - air, Teflon, polystyrene, etc. and a great shield.
On my system here I am using the manufacturers cables on both of my tonearms, as they also match the cartridges I am using. However, I will say that ideally you would find a suitable interconnect that matches the cartridge you are using. If you ever switch to another cartridge, reevaluate the interconnect parameters before you hook everything up. You might just need a different interconnect.
