Digital TV SCTE 35 signal
To determine if a channel has SCTE-35, you will need to have the Program Map Table (PMT) recorded. From the PMT, you should be able to find the Packet Identifiers (PIDs) of all of the streams associated with the channel you are interested in. There will be a PID for the video and at least one audio PID. If SCTE-35 is present, there will be at least one PID with a stream type of 0x52.

Keep in mind, the PMT and the SCTE-35 PID will either need to be in the clear or you will need to be able to decrypt the conditional access.

The easiest way to check all of this is with a transport stream analyzer. Most of the freely available ones, like DVB Inspector, will show you the PMT. However, you will probably need a commercial analyzer to get it to display something more than just the raw SCTE-35 bytes.