They introduced "Pay as You Go" (direct tolling) so you don't need to hold a balance anymore. You'll basically just have a negative balance until they charge your card twice a month. Has surprisingly actually worked for me, and confirms that accounts can go negative now. I can choose to add funds or just wait for the charge to go through.
TReO, the tolling system for the Port Mann bridge in BC before it was detolled, was built by a Vancouver-based company: https://oxd.com/work/treo-tolling-website/
And run by the TIC: https://www.ticorp.ca/
Second, every tolling system is different. Sometimes the accounting (often called the back office system) is contracted out, sometimes it is performed in-house by the tolling agency.
Source: I work for one of the better quality contractors.
Between:
* The implementation delays https://www.spokesman.com/stories/2012/jul/19/wsdot-reaches-...
* The payment issues https://www.seattletimes.com/seattle-news/transportation/sta...
* The customer support issues
* the sensor issues (admittedly those may be on the state and not ETC/ETAN, unclear)
and more the state abandoned its contract with ETC in favor of one with ETAN, which took the system offline for two weeks to switch over and admittedly hasn't been much better (https://www.seattletimes.com/seattle-news/transportation/wsd...).
God forbid we let the state hire a few local SWEs (Seattle doesn't have any of those) to write and maintain a system instead of paying $30M every few years plus a cut of tolls to whatever Texas contractor gave the most perks to a WSDOT exec.
There's a good reason that the systems themselves cost so much money. Heck, it costs an arm and a leg just for the routine maintenance permits! The CI/CD, security, data persistence, data provenance, latency, and agency interop requirements are absolutely insane. Trust me, it's more than just a few SWE can handle.
Lastly, it's definitely not about any under-the-table dealings. There's just a huge amount of work! When deciding to whom to award the contract, they do background checks on key company people, look at past contracts, etc.
That's the reality of the situation.
In Washington State who has the "Good to Go" system. Its deployment has been full of quirks, my favorite of which was that if your balance ever went negative (say you had it set up to replenish at $5 but got a $10 toll) the system would refuse to charge you (even when you had a payment method on file or went to their website) and you had to call in and talk to a human to fix it.