Bukkit

Transporting villagers and pets long distances is difficult enough without having to dismount them at every portal. With this plugin, all entities riding vehicles will instantly teleport through portals.

How does it work? 

This plugin listens all to vehicle movement, checks if it is in a portal, and, if so, tells each passenger to dismount and remounts them once the vehicle teleports.

There are no teleport calculations - meaning RTP should be compatible with any other portal or teleportation plugins that you have installed.

Caveats/Additional info:

• Currently, only minecarts are supported. I plan to add horses, boats, etc, in future updates.
• Portals that cut across the X or Z axis may experience inconsistent teleports. This is a bug with vanilla Minecraft, see https://bugs.mojang.com/browse/MC-187330.
• Vehicles will instantly teleport regardless of the portal cooldown. 
• Players will instantly teleport if they are riding a vehicle.
• There are no portal permission checks - if you have modified the permissions, directly or through plugins, this plugin may adversly affect them.
• There is a chance that the minecart will not teleport. Increase the minimum velocity config if this frequently occurs.
• Currently, there is no garbage collector. Minecarts which are destroyed will not be removed from the plugin's tracker - for now. The memory used by this is insignificant, though. 
• The plugin may not detect that a minecart has finished teleporting. Usually you just have to wait for one of the passengers to rotate/move slightly in minecart, but if not, just give the vehicle a nudge. To this end, it is possible that the passengers will wander off.
• The plugin's tracker is not saved. If a vehicle is mid-teleport during server shutdown, those passengers will not remount the vehicle post-teleport.
• This plugin listens to the VehicleMoveEvent which may affect server performance.