I think that you could try one of the method I’m using to export facial animation data from UE4, doing the opposite.
UE4 to Maya - Facial Animation Pipeline
In the video you can see realtime facial animation that is then exported via FBX to Maya, where I’m using a proxy rig with 52 joints named after each blend shape, connected to each morph target in UE4, so that every time a blend shape is active( value from 0 to 1 ) the correspondent joint on the “proxy rig” is moved on the Z axis ( value from 0 to 1 ).
I’m using sequence recorder to record the skeletal animation, then when imported into Maya I’m using a Set Driven Key script that apply a retargeting from those proxy rig joints to the Blend Shape facial rig.
I guess you can do the opposite, meaning that in Maya you can have the Blend Shape facial rig driving the proxy rig joints, then in UE4 you can create a BP setup where the proxy rig joints value are driving the Blend Shape rig, so that you can have a realtime link between Maya and UE4, using a hack to drive the blend shape facial rig.
Hope this helps