Summoning any type of minecart with invisibility effect summons a visible minecart.
/summon Minecart ~ ~ ~ {ActiveEffects:[{Id:14,Amplifier:2,Duration:10000000}]}
/summon MinecartHopper ~ ~ ~ {ActiveEffects:[{Id:14,Amplifier:2,Duration:10000000}]}etc.
Minecarts can't have status effects applied to them; Only mobs can. Not a bug.