I want to connect a Partner PBX interface T1 to a Legend PBX with analog ports. When connecting the 2410 to a PBX, does one side need to be trunks and one side stations, or can they both be trunks?

This is a valid application using an MVP2410 on the T1 side and an MVP210, 410, 810 on the analog station / CO port side. Before deciding which PBX interface to use, you should consider the number of concurrent calls required and the features available for each interface type. CO Vs. Analog Station ports may allow different dial/answer features which should be considered.