do you have to pay anythign each time you use the service or if they find any other blockage or broken pipe do they cover ?

Also for the first time, you have no way of knowing if it was the current tenants or a previous one and something happened later to cause the blockage.

For example, my lease states “Tenant shall be charged for repair of drain blockages or stoppages, unless caused by defective plumbing parts or tree roots invading sewer lines.”So, having not read your lease, we couldn’t say for certain who is responsible for the cost.

However, the blockage continued as it was, so he had to come out again and have a look the week after.

The City has made it very clear to property owners that if they are required to clear a lateral due to a blockage resulting from wipes, the property owner will foot the entire bill.We have likewise made it very clear to our tenants that the use of wipes is prohibited in our properties and any costs incurred to clear an obstruction resulting from their use will be passed along to the tenant.We had one instance in November where tenants use of wipes managed to clog a backflow valve at one of our properties.  

While fix underway plumber also stated blockage was caused by a kids ball in the line.

If a garbage disposal stopped spinning but makes a bit of noise showing the electricity is on (likely something is blockage it but unsure), who is supposed to pay for the technician to repair it: the landlord or the tenant?

Put a grate of some sort on that intake so that doesn't happen again, pay for the repair, then let the tenant know that if there is every a blockage of that intake it will be their responsibility to pay because that is a result of them not maintaining the grounds.

Changed the lease to basically say that as the owner I am responsible to ensure operational status of all the facilities and, at the time of your occupancy, electrical, heating, cooling and all plumbing fixtures are operational.If there is any blockage of the plumbing, it is due to your negligence and therefore your responsibility to have it cleared. 

Of course, if it's something other than just a simple blockage or there is damage to the line it will cost moreI've never heard the term hydro scrub.