No worries, to judge from the number of responses I'm not making much sense either.
I am not real clear on the distinction between samatha (calm abiding) and vipassana (insight). In the past I identified samatha with jhana and deep, narrowly focused fixed concentration. I identified vipassana with satipatthana and moment-by-moment, fluid, and expansive observation. That sort of works, but I no longer see such a clear distinction.
I understand cultivation of Brahma Viharas in terms of samma vayama -- as the 3rd of the 4 struggles, the development of wholesome and liberating mental states. Once these mental states are aroused, continued practice would be maintenance. They relate to the 1st (blocking) and 2nd (abandoning) in that they counter unwholesome mental states. The first three directly counter hostile (dosa) mental states. Metta bhavana counters vyapada / enmity, karuna bhavana counters cruelty, mudita counters issa / envy. As many have discussed, they also counter near enemies related to lobha, such as kama and raga. Equanimity would seem to directly counter various mental states related to avarice (lobha), such as pride (mana / mada), and attachment (raga) as well as mental states related to confusion (moha), such as restlessness and agitation. It would also counter the near ememy of apathy.
This could be samatha practice, in that the mind is being calmed; hostile, greedy, and agitated states are being replaced by friendly, generous, and poised / objective mental states. I now relate cultivating and maintaining the Brahma Vihara more to preliminary concentration in that the Brahma Vihara help overcome the five hindrances. Also as a gradual practice to acquire merit.