С regex:
x="max. bit rate: ('2.5 MBit/s', '16.7 MBit/s')" [[ $x =~ .*\'(.*)\'.*\'(.*)\'.* ]] && echo "${BASH_REMATCH[1]} ${BASH_REMATCH[2]}"
Выход:
2.5 MBit/s 16.7 MBit/s