You may buy as many subscriptions as you want, except for VIP subscription.
For example:
1. CWS = serv2 XXXX1 login password 01 02 03 04 05 06 07 08 09 10 11 12 13 14 wan cardserv - this is your Polsat subscription
2. CWS = serv2 XXXX2 login password 01 02 03 04 05 06 07 08 09 10 11 12 13 14 wan cardserv - this is your Cyfra+ subscription
3. CWS = serv2 XXXX3 login password 01 02 03 04 05 06 07 08 09 10 11 12 13 14 wan cardserv - this is your whatever else subscription etc., etc.
But, if you buy any VIP subscription which includes all the above subscriptions (for example, VIP Poland), all your above subscriptions will be stopped.
Of course, each subscription is different by its port No. All of them have different ports.
If you use newcamd.list (for linux-based receivers), each subscription has its own CWS line with different port. Receiver selects the required server, port etc. by itself and is connecting to the required server.
You may even use subscriptions from other cardsharing provider. CWS lines will not interfere with each other, because each CWS line has its unique address.