
A couple of the bio's for Optibus Prime and Megatren are as follows:
MEGATREN - Mega is a prefix meaning large or huge; Tren when translated into English means Train, so Megatren stands for Big Trains (i.e. MRT and LRT). This is one of the most popular transportation vehicles Filipinos use, because it’s fast and easily accessible to almost all of the key cities in Manila.
OPTIBUS PRIME - While the buses in Hong Kong are made of two stories, here in the Philippines it’s only one. This is widely used by many, especially when commuting to provinces accessible by land.
To view the original post on these fan made TF's and see the origins listed for each, just click here.