ISP broadcasting all IP-packets, so I can see traffic of other clients from ISP

It has been a while since I consulted to the telecom industry so I am going off of what is still likely.

For DSL, this is sub-par. You should never see traffic destined for another IP address. I would check with your provider. This is not a standard configuration and it is likely that there are some settings in the RedBack that are not right. Each connection should be segmented and the bandwidth you are paying for by contract is being wasted. DSL connections are frame connections when you whittle through all of the protocols. This means that your frame connection must only see the traffic for your segment.

For Cable, this is normal. Cable is segmented by neighborhoods depending upon area saturation. A neighborhood could be many miles or one block. This is normal since cable is not a frame connection but based upon broadcast standards much like ethernet over thin-net/thick-net back in the day. Your cable router may or may not enforce network segmentation depending upon the router, either by age or by model. Cable connections almost always see traffic on the WAN side that is not intended for the LAN. But sometimes WAN traffic can be seen on the LAN side. This is not unusual even today with the larger carriers.

No, this is not normal. Contact your provider to resolve this issue. When they can't, switch away ASAP.