LAC does not have any built-in SOAP capabilities, but that does not mean that it cannot talk to SOAP -- it just means that you'll have to do the work yourself, or use something like the CA API Gateway, which can do some translation between SOAP and REST.
One way to have LAC talk to a SOAP API is simply to add a Java library for said SOAP API (usually generated from the WSDL) to your classpath (e.g. Tomcat/lib or whatever) and make calls to that library from your LAC logic (rules, events, etc...). It would typically look something like:
var DefaultWebService = Java.type("com.acme.service1.soap.DefaultWebService");
var defaultWebService = new DefaultWebService();
var res = defaultWebService.getDefaultWebServiceHttpSoap11Endpoint().login("webservice","dadsadasdasd");
etc...
You can also use the standard Java SOAP API, something like:
var SOAPConnectionFactory = Java.type("javax.xml.soap.SOAPConnectionFactory");
var soapConnectionFactory = SOAPConnectionFactory.newInstance();
var MessageFactory = Java.type("javax.xml.soap.MessageFactory");
var messageFactory = MessageFactory.newInstance();
var soapMessage = messageFactory.createMessage();
etc...
There are lots of examples available on the web, and they're trivial to translate to JavaScript.