Towards the 5G vision of massive access exploding the growth in data traffic, spectrum refarming and reallocation are considered key enabling technologies. Using spectrum reallocation (SR) with the spectrum originally assigned to a Radio Access Technology (RAT) and the the remaining to use spectrum reallocation in the context of multi-RATs (m-RAT). For example, GSM, HSPA and UMTS technologies to be underutilized due to the migration of subscribers to 4G networks are considered in the m-RAT application scenario. To this end, efforts are made in order to deploy m-RAT systems, where the spectrum assigned to m-RATs can be efficiently redistributed and utilized by the involved RATs. In this work, we assume a HSPA/LTE-A m-RAT that provide Carrier Aggregation (CA) too, and propose specific functionality in order to coordinate the operation of both RATs regarding the spectrum assignment and resource allocation. Results show that by assigning spectrum to cover a minimum performance requirement for HSPA, there is a significant performance improvement for LTE-A. Moreover, when spectrum assignment is performed jointly with resource allocation between the involved RATs, the throughput results are higher for both HSPA and LTE-A users.