According to the article, IMDA will reallocate the band via auction/bidding. Seems like they did the auction in 2021. Dont know the result.
https://www.imda.gov.sg/resources/p...pectrum-bands-to-all-mobile-network-operators
IMDA intends to allocate the new spectrum via auction, open to all existing MNOs if the MNOs wish to participate. Through the market-based approach, bidders will get the flexibility to decide how much spectrum they require. All 2.1 GHz spectrum right holders must meet baseline regulatory requirements, consistent with the requirements on holders of the first tranche of 5G spectrum allocated through IMDA’s 5G CFP held in 2020. IMDA intends to hold the auction towards the end of 2021. As part of the auction design, IMDA intends to set aside some 2.1 GHz spectrum for the continued provision of 3G services in Singapore, for consumers who choose to continue to use these services.