migrate FreeBSD jails to linux

we are running some jails in FreeBSD 10 and the decision has been made to decommission the FreeBSD server and migrate all the jails to Linux environment Red Hat 6 or 7.

Is there a straight forward way of migrating BSD jails to linux -- as containers that can be run via docker

or any other way to convert BSD jails to containers and pull/run via docker again.

Any other way of doing it ? I'm unsure whether this is actually possible or not because I tried reading on google but has not come across anything like that.
Docker containers are basically stripped down Linux machines. There's no easy way to "convert" one to the other, you'll have to build things from scratch.
Before we go any further I will state for the record that I run at work RHEL 6 (I run bunch of KVM instances), RHEL 7 (only computing nodes, desktops with VirtualBox instances), and FreeBSD 10+jails using iocage. As much as I hate systemd I would suggest that you use RHEL 7 as it is getting harder to update software on RHEL 6 to reasonably new versions.

The answer to your original question is simply NO. There is no easy way to migrate Jails which are OS level virtualization to any virtualization RHEL supports (choice is really KVM or VirtualBox both belonging to the group of Emulator virtual technologies). Dockers are just sandboxes and I hate them with passion. They breaking stuff left and right and are notoriously insecure. I should also mentioned that although theoretically possible to run Xen Dom0 kernel on RHEL I would discourage you from doing it as Linux is very hostile to non-native kernel modules.

So you will have essentially to do fresh installation of your jail instances and choice is KVM or VirtualBox. Both are equally insecure. I strongly prefer KVM over VirtualBox which we use on desktops to run Internet Explorer and test our web applications.

Since I am giving advises here I would discourage you from using ZFS on RHEL for the same reason as Xen.
Unfortunately for you, this is a Linux question about a Linux problem and, therefore, you should ask this on a Linux forum.

FreeBSD forums rules of the road:
We will not allow technical/support questions about any operating system other than FreeBSD anywhere on this forum. That includes the Off-Topic forum. Always ask technical/support questions about other operating systems on the forums or mailing lists associated with those operating systems.
Insofar as options may exist to allow exporting and/or conversion and/or importing of FreeBSD jails to other technologies, this is allowable. If they do not, that is information too.
It's a valid question but the OP is not aware that the FreeBSD "world" (userland binaries and applications) has almost nothing in common with the Linux equivalents except for fact that on the surface both implement roughly the same set of utilities and many of the same applications are available on both. FreeBSD has its own ABI that Linux does not support (with the exception of Debian's kFreeBSD) and so trying to run FreeBSD jails under Linux is not going to work.
we are running some jails in FreeBSD 10 and the decision has been made to decommission the FreeBSD server and migrate all the jails to Linux environment Red Hat 6 or 7.
That's a shame but it's probably a decision that has been made by upper-management and there's nothing you can do about that.

As has been noted already there's just no way to convert a FreeBSD jail to some technology on Linux. But there may be other solutions. What sort of services are currently running on the FreeBSD jails?