yes its basically a spline.
would be interesting to do and not hard mathematically to deploy as a trap (trap_curveTrace with something like angle drifts for anchor midpoints? mutiple? this?), but i can't for the life of me figure out who would want a railgun that curves; unless its predicting who's gonna get hit by something like a mortar from the sky.
ET does that i think with their mortar stuff. One big splined curve. Someone fires a weapon and the curve is projected to wherever the endpoint is from the top down, faking a projectile's natural curve through space and gravity. Mappers would have to design for it that way, make sure theres always sky above all structures. WFA maps don't do that for performance/efficiency reasons.
it's not that hard to do. After doing lens refractions the way i did em, anything is possible.