Twin cities are a special case of two cities or urban centres that are founded in close geographic proximity and then grow into each other over time, losing most of their mutual buffer zone. To be considered twin cities, the cities involved have to have a similar administrative status and somewhat comparable sizes.
Raipur and Bilaspur are approximately 100km apart. They may or may not grow into each other, which can't be determined due to the negligible tendency of the suburban settlements and the expansion of cities towards each other. Though they have similar administrative status and comparable sizes, the fundamental points are ruled out. Hence, under current circumstances, Raipur and Bilaspur can't be called Twin Cities. The Raj can start at...
more... least from Durg, which can be termed as "nearest to the state/UT capital city" to satisfy the definition and it can run via Raipur, which is the nearest to the new capital city "Atal Nagar (previously Naya Raipur)". Thus, BSP Raj is proven as an anomaly.
Moreover, I add that it is not correct to think that what hasn't happened in the past will not happen in the future, especially, in scenarios like Imagination Trains, where the possibilities in the future are kept in mind. Naganahalli was announced to be a new terminal for Mysuru, yet I didn't see any IMG train starting from Naganahalli (expecting some in the near future) and people laughed at me when I introduced an IMG with all 3A coaches and it is not a Garib Rath, but a new AC train (today we have the HumSafar). I heard from the same IRI that no more new Jan Shatabdis, yet we got a new one. Things which are highly impossible, controversial when compared to the current scenario and future prospectus can be denied (things like Barkichampi as a new Terminal for Ranchi, Hubballi - Dharwad gets its first Rajdhani being a new capital city, etc.,.). Pros first, cons next. Thank You.