The quarantine was originally set to begin on July 22. Later it was brought up to July 20. Neither team would have been able to arrive in Dhaka by that date because Bangladesh were on tour in Zimbabwe and Australia were on tour in the West Indies. So the BCB and CA agreed that so long as their players remained inside a secure bio-bubble - Bangladesh in Harare and Australia in Gros Islet and Bridgetown - it could count towards their quarantine time in Dhaka.
As a result, the BCB contacted Rahim and asked him to stay back in Zimbabwe for the entire duration of the tour. Initially, he he was meant to return home after the end of the ODI leg. But, complications arose when Rahim's parents fell sick and he had to fly home early. In the end, he was unable to make the quarantine deadline due to family commitments and when he did report in, on July 22, he was told it won't work.
"Mushfiqur (Rahim) wanted to play the series," Akram Khan, BCB's cricket operations chairman, said, "But he missed the quarantine by a couple of days. His parents are sick, so he had to leave the Zimbabwe tour. But the [10-day] quarantine is part of our agreement with Cricket Australia, so we couldn't include him. They didn't agree to Mushfiqur entering quarantine two days after it began. It is disappointing but one can't do much about these things."
The rest of the Bangladesh players, upon arrival in Dhaka from Harare on July 27, will go straight from the airport to the hotel. Match officials, liaison officers, hotel staff and drivers are among those who have already gone into mandatory hotel quarantine. Bangladesh and Australia will play five T20Is from August 3 to 9. The hosts are already without Tamim Iqbal, who is nursing a knee injury and is out of competitive cricket for at least eight weeks.
Mohammad Isam is ESPNcricinfo's Bangladesh correspondent. @isam84