So without further ado here are the steps:
In Maya, imagine your hand-animated camera is named "CAM" and make sure you're at frame 1.
Step 1 - Duplicate CAM and add an "_export" to the name for identification.
Step 2 - Parent CAM_export to CAM. (Parent_CAM being the child of CAM.) This step would "zero" out the transformations in CAM_export's channel box naturally.
Step 3 - Rotate CAM_export in the Y-axis by 90 degrees.
Step 4 - Unparent CAM_export from CAM. This step would "give back" the original transformations to CAM_export but with an addition of 90 degrees to the value of Y-axis.
Step 5 - Parent constraint CAM_export to CAM so that CAM_export will "absorb" the keyed attributes of CAM. ("Maintain Offset" checked)
Step 6 - [Key > Bake Animation] for CAM_export. ("From Channel Box" checked and set Start/End time range, as we only need to bake translate and rotate values.)
Step 7 - [File > Game Exporter] CAM_export into the desired Unreal Project folder as FBX. (Animation checked)
Moving over to Unreal:
Step 1 - Cinematics > Add Level Sequence
Step 2 - In the Sequencer, change the fps to 25fps. (My usual framerate.).
Step 3 - Set your desired start and end values in the timeslider,
- followed by going to playback options, setting the Start and End values again.
- Lastly, check the locked option.
Step 5 - Right click on the newly created CineCameraActor and click import.
Step 6 - Import the CAM_export.fbx file. (Uncheck "Reduce Keys" in the import options.)
Step 7 - With the maya camera now imported in to the Unreal Sequencer, you may delete the CineCameraActor.
Step 8 - Click the + sign on the Camera Cuts layer and select the CAM_export as the existing binding.
Step 9 - Render
And there you have it, idiot proof method of exporting animated cameras from Maya into Unreal without tearing your hair out!