It seems that service containers are now regarded as the best-fit solution for replacing docker-compose in Pipelines:

BCLOUD-12757

However, by only supporting service containers, any use of docker-compose for local dev environments, requires developers to then maintain 2 duplicitous configuration files for virtually the same purpose (Pipelines service & Dockerfiles).

In my case, we have a complex docker-compose setup which spins up our local dev environment as well as our CI environment for running tests. If we want to migrate from Bamboo Server to BB Pipelines, I now need to start maintaining Pipelines Services in addition to docker compose.

One potential short term solution to this would be to adding functionality to allow importing Dockerfiles into service container definitions. At least then there's no need to maintain duplicitous pipelines/composer definitions.

However, ideally allowing docker-compose to be used would be the best-case scenario...

Update:
Even with latest version of docker client 20.10.24 in service containers does not bundle with docker compose

Example:
docker client 20.10.24

Management Commands:
 builder   Manage builds
 buildx*   Docker Buildx
 compose*  Docker Compose

docker client 20.10.24 on Bitbucket pipelines

Management Commands:
  builder     Manage builds
  config      Manage Docker configs
  container   Manage containers
  context     Manage contexts