Does Plug and Play Scada have a Tariff Engine?

Yes.
Plug and Play Scada has a very flexible and powerful Tariff Engine.
Some of the supported features are TOU tariffs, tariff banding, consumption of any of up to 6 consumptive registers - or a combination thereof - per meter (including forwards and backwards energy flow); as well as multiple kinds of Demand (RMS kVA or integrated kVA over a profile period); configurable profile length, e.g. 1-60 minutes per period, international currencies and configurable tax rates and types.
Some more supported features include co-incident maximum demand (with multiple configurable ways to divide it between sub-metering points); excess reactive energy charge, specialized tariffs for different municipalities, e.g. Tariff D surcharge for Ekurhuleni and so on, a fixed charge per Breaker Size or per month or per day, banding per month or day or demand, and a lot more.
Inherent in the Billing Engine is also features like check metering (effectively gives a check metering report PER PROFILE PERIOD); Summation metering, as well as dividing a single or a group of meters according to the square meter area of the meter accounts, or other criteria.
Multiple Meter Account Numbers per Meter Account are also supported with a view to reconciling meter accounts to external accounting systems, that often need more than one identifier per account. Plug and Play Scada currently supports about a dozen different exports to various systems, including generic exports with a line item per meter account, or per meter account detail line.
A very basic feature is also Provisional Bills for any selectable period, as well as Tariff Comparisons for any selectable period.
The developers of Plug and Play Scada is expanding the functionality of the Tariff Engine all the time, to keep up with the complex and intricate tariffs that often see the light in South Africa, and elsewhere. Please feel free to post your comments if you have any ideas of how we can expand it.

Here is an example of setting up a tariff line item for co-incident Maximum Demand.
The account that determine when the Maximum Demand is during the month should be the Main Incomer, or something that approximates it, for example a check Meter Account, or possibly a Summation Meter Account (an account that includes all the units in the residential development, for example).
The best way in terms of getting payment, is normally to charge for the MD % in proportion to the tenant's % kWh usage (% kWh of the meter account billed to the kWh used by the main incomer); although in some cases it might be deemed to charge each tenant for their MD on the same half hour as the period identified on the Main Incomer, so in that case select 'Keep kVA for MD period.