Multi-tower support is there, but not all networks support it and not all CA-capable terminals support it.
However, I don't think B20 intraband CA is supported at all (even for single-tower setups). And CA only works for cells usung different frequencies. LTE networks are SFN (single-frequency nerworks) which means adjacent towers use exactly same frequency (carrier) and due to interference issues CA is not feasible in such case.
Whether you'd actually gain something by connecting to both towers depends on geometry: if by using narrow-beam high-gain antennae you can make signal from chosen tower dominant, then yes. If both towers are in approximately same direction, then probably not.