Sharing fiber with /29 mask

[thuizt]

Hello,

We have here at least 3 or 4 companies all with their own ADSL broadband connection behind a pfSense box. Everyone happy :-)
We have the possibility to share a fibre line with a small public ip subnet. (/29)

We thought about placing a pfSense at the fibre line and route to each pfSense firewall.

Nearly all companies have IPSec connections on their firewalls to customers / relations / branches etc.

Can someone please hint us on how to achieve this ?

Thanks